#include <iostream>
#include <fstream>
#include <vector>
#include <map>
#include <algorithm>
#include <cassert>
#include <queue>
#include <set>
#include <iomanip>
#include <complex>

using namespace std;
using ll = long long;
using ld = long double;

class huge
{
private:
    int sign; // -1 daca numarul este negativ, +1 daca este pozitiv
    string digits; // cifrele numarului, stocate in ordine inversa

public:
    // initializare implicita cu 0
    huge()
    {
        digits = "0";
        sign = 1;
    }
    // initializare prin intermediul unui sir de caractere
    huge(string s)
    {
        int i;
        if (s.front() == '-')
            sign = -1,  i = 1;
        else if (s.front() == '+')
            sign = 1,  i = 1;
        else
            sign = 1,  i = 0;

        for (int j = s.size() - 1; j >= i; --j)
            digits.push_back(s[j]);
    }
    // initializare prin intermediul unui caracter
    huge(char c)
    {
        sign = 1;
        digits.push_back(c);
    }
    // initializare prin intermediul unui numar intre -2^31 si 2^31 - 1
    huge(int n)
    {
        if (n < 0)
            sign = -1;
        else
            sign = 1;
        n = std::abs(n);
        do
        {
            digits.push_back(n % 10 + '0');
            n /= 10;
        }
        while (n);
    }
    // conversie la sir de caractere
    operator string() const
    {
        string ans;
        if (sign == -1)
        {
            ans.resize(1 + digits.size());
            ans.front() = '-';
            reverse_copy(digits.begin(), digits.end(), ans.begin() + 1);
            return ans;
        }
        else
        {
            ans.resize(digits.size());
            reverse_copy(digits.begin(), digits.end(), ans.begin());
            return ans;
        }
    }
    // comparator ==
    friend bool operator == (const huge& a, const huge& b)
    {
        return (a.sign == b.sign && a.digits == b.digits);
    }
    // comparator <
    friend bool operator < (const huge& a, const huge& b)
    {
        if (a.sign == -1 && b.sign == 1)
            return true;
        if (a.sign == 1 && b.sign == -1)
            return false;
        if (a.sign == -1 && b.sign == -1)
            return (b.abs() < a.abs());
        if (a.sign == 1 && b.sign == 1)
        {
            if (a.digits.size() < b.digits.size())
                return true;
            if (a.digits.size() > b.digits.size())
                return false;
            for (int i = a.digits.size() - 1; i >= 0; --i)
                if (a.digits[i] < b.digits[i])
                    return true;
                else if (a.digits[i] > b.digits[i])
                    return false;
            return false;
        }
    }
    // comparator <=
    friend bool operator <= (const huge& a, const huge& b)
    {
        return (a < b || a == b);
    }
    // comparator >=
    friend bool operator >= (const huge& a, const huge& b)
    {
        return !(a < b);
    }
    // comparator >
    friend bool operator > (const huge& a, const huge& b)
    {
        return !(a <= b);
    }
    // valoarea absoluta
    huge abs() const
    {
        huge ans = *this;
        ans.sign = 1;

        return ans;
    }
    // opusul (inversul in raport cu adunarea)
    huge operator - () const
    {
        if (digits == "0")
            return *this;

        huge ans = *this;
        ans.sign *= -1;
        return ans;
    }
    // suma a 2 numere
    huge operator + (const huge& b) const
    {
        if (sign == -1 && b.sign == -1)
            return -(this->abs() + b.abs());
        if (sign == -1 && b.sign == 1)
            return b - this->abs();
        if (sign == 1 && b.sign == -1)
            return *this - b.abs();
        if (sign == 1 && b.sign == 1)
        {
            huge ans;
            ans.sign = 1;
            ans.digits = "";
            int cnt = 0, i;
            for (i = 0; i < std::min(digits.size(), b.digits.size()); ++i)
            {
                int sum = digits[i]-'0' + b.digits[i]-'0' + cnt;
                ans.digits.push_back(sum%10 + '0');
                cnt = sum/10;
            }
            for (; i < digits.size(); ++i)
            {
                int sum = digits[i]-'0' + cnt;
                ans.digits.push_back(sum%10 + '0');
                cnt = sum/10;
            }
            for (; i < b.digits.size(); ++i)
            {
                int sum = b.digits[i]-'0' + cnt;
                ans.digits.push_back(sum%10 + '0');
                cnt = sum/10;
            }
            for (; cnt; cnt /= 10)
                ans.digits.push_back(cnt%10 + '0');
            return ans;
        }
    }
    // diferenta a 2 numere
    huge operator - (const huge& b) const
    {
        if (sign == -1 && b.sign == -1)
            return b.abs() - this->abs();
        if (sign == -1 && b.sign == 1)
            return -(this->abs() + b);
        if (sign == 1 && b.sign == -1)
            return *this + b.abs();
        if (sign == 1 && b.sign == 1)
        {
            if (*this < b)
                return -(b - *this);
            huge ans;
            ans.sign = 1;
            ans.digits = "";
            int i;
            bool cnt = 0;
            for (i = 0; i < std::min(digits.size(), b.digits.size()); ++i)
            {
                if ((digits[i]-'0') - (b.digits[i]-'0') - cnt < 0)
                {
                    ans.digits.push_back((digits[i]-'0') - (b.digits[i]-'0') - cnt + 10 + '0');
                    cnt = 1;
                }
                else
                {
                    ans.digits.push_back((digits[i]-'0') - (b.digits[i]-'0') - cnt + '0');
                    cnt = 0;
                }
            }
            for (; i < digits.size(); ++i)
            {
                if ((digits[i]-'0') - cnt < 0)
                {
                    ans.digits.push_back((digits[i]-'0') - cnt + 10 + '0');
                    cnt = 1;
                }
                else
                {
                    ans.digits.push_back((digits[i]-'0') - cnt + '0');
                    cnt = 0;
                }
            }
            while (ans.digits.size() != 1 && ans.digits.back() == '0')
                ans.digits.pop_back();
            return ans;
        }
    }
    // produsul a 2 numere
    huge operator * (const huge& b) const
    {
        if (*this == huge(0) || b == huge(0))
            return huge(0);
        huge ans;
        if (sign + b.sign == 0)
            ans.sign = -1;
        else
            ans.sign = 1;
        ans.digits.resize(digits.size() + b.digits.size(), '0');
        int cnt, i, j;
        for (i = 0; i < digits.size(); ++i)
        {
            cnt = 0;
            for (j = 0; j < b.digits.size(); ++j)
            {
                int sum = (ans.digits[i+j]-'0' + (digits[i]-'0') * (b.digits[j]-'0') + cnt);
                ans.digits[i+j] = sum%10 + '0';
                cnt = sum/10;
            }
            if (cnt)
                ans.digits[i+j] = (ans.digits[i+j]-'0' + cnt) + '0';
        }
        while (ans.digits.size() != 1 && ans.digits.back() == '0')
            ans.digits.pop_back();
        if (ans.digits == "0")
            return huge(0);
        return ans;
    }
    // catul impartirii a 2 numere
    huge operator / (const huge& b) const
    {
        if (*this == huge(0))
            return huge(0);
        huge ans, A = this->abs(), B = b.abs();
        if (A < B)
            return huge(0);
        huge dei, inm;
        dei.digits = "";
        ans.digits = "";
        int i;
        for (i = digits.size() - 1; ; --i)
        {
            dei.digits.insert(dei.digits.begin(), digits[i]);
            if (dei >= B)
                break;
        }
        for (i--; i >= -1; --i)
        {
            for (int j = 0; j <= 9; ++j)
            {
                inm.digits[0] = j+'0';
                if ( !(B * inm <= dei) )
                {
                    inm.digits[0]--;
                    break;
                }
            }
            ans.digits.push_back(inm.digits[0]);
            dei = dei - B*inm;
            if (dei.digits == "0")
                dei.digits = "";
            if (i >= 0)
                dei.digits.insert(dei.digits.begin(), digits[i]);
        }
        if (sign + b.sign == 0)
            ans.sign = -1;
        else
            ans.sign = 1;
        reverse(ans.digits.begin(), ans.digits.end());
        return ans;
    }
    // restul impartirii a 2 numere pozitive
    huge operator % (const huge& b) const
    {
        return *this - *this / b * b;
    }
    // citire prin intermediul stream-urilor
    friend istream& operator >> (istream& in, huge& n)
    {
        int i;
        string nr;
        in >> nr;
        if (nr.front() == '-')
            n.sign = -1,   i = 1;
        else if (nr.front() == '+')
            n.sign = 1,   i = 1;
        else
            n.sign = 1,   i = 0;
        if (nr == "-0")
            n.sign = +1;
        n.digits.resize(nr.size() - i);
        reverse_copy(nr.begin() + i, nr.end(), n.digits.begin());
        return in;
    }
    // scriere prin intermediul stream-urilor
    friend ostream& operator << (ostream& out, const huge& n)
    {
        if (n.sign == -1)
            out << '-';
        for (int i = n.digits.size() - 1; i >= 0; --i)
            out << n.digits[i];
        return out;
    }
};

huge calcComb(int n, int k) {
    if (n < k) {
        return 0;
    }
    if (k > n - k) {
        k = n - k;
    }
    huge comb = 1;
    for (int i = 1; i <= k; i++) {
        comb = comb * (n - i + 1);
    }
    for (int i = 1; i <= k; i++) {
        comb = comb / i;
    }
    return comb;
}

void solve() {
    int n, d;
    huge a, b;
    cin >> n >> d;
    cin >> a >> b;
    a = b - a;
    int ans = 0;
    for (int i = (1 << 9); i; i >>= 1) {
        int k = ans + i;
        huge badComb = calcComb(n - (k - 1) * d, k);
        huge totalComb = calcComb(n, k);
        if (totalComb * a < badComb * b) {
            ans += i;
        }
    }
    cout << ans + 1 << '\n';
}

signed main() {
#ifdef LOCAL
    assert(freopen("test.in", "r", stdin));
    assert(freopen("test.out", "w", stdout));
#else
    assert(freopen("bile2.in", "r", stdin));
    assert(freopen("bile2.out", "w", stdout));
#endif
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    int nrt = 1;
    //cin >> nrt;
    while (nrt--) {
        solve();
    }
    return 0;
}