#include <stdio.h>

#define FIN "bile2.in"
#define FOUT "bile2.out"
#define ll long long

int N, D;
ll A, B, cnt[64][64], comb, res;

int main(void)
{
    int i, j;

    freopen(FIN, "r", stdin);
    freopen(FOUT, "w", stdout);

    scanf("%d %d %lld %lld", &N, &D, &A, &B);

    for (comb = i = 1; i <= N; ++i)
    {
        res = 0;
        for (j = 1; j <= N; ++j)
        {
            cnt[i][j] = i == 1 ? 1 : cnt[i][j-1];
            if (j-D-1 > 0) cnt[i][j] += cnt[i-1][j-D-1];
            res += cnt[i][j];
        }
        comb *= N-i+1; comb /= i;
        if (res*B <= (B-A)*comb)
            break;
    }
    printf("%d\n", i);

    return 0;
}