#include <bits/stdc++.h>
#define startt ios_base::sync_with_stdio(false);cin.tie(0);
typedef long long  ll;
using namespace std;
#define vint vector<int>
#define all(v) v.begin(), v.end()
#define MOD 1000000007
#define MOD2 998244353
#define MX 1000000000
#define MXL 1000000000000000000
#define PI (ld)2*acos(0.0)
#define nax 200005
#define pb push_back
#define sc second
#define fr first
#define int long long
#define endl '\n'
#define ld long double
#define NO cout << "NO" << endl
#define YES cout << "YES" << endl
int ceildiv(int one, int two) {if (one % two == 0) {return one / two;}else {return one / two + 1;}} int power(int n, int pow, int m) {if (pow == 0) return 1;if (pow % 2 == 0) {ll x = power(n, pow / 2, m);return (x * x) % m;}else return (power(n, pow - 1, m) * n) % m;} int gcd(int a, int b) { if (!b)return a; return gcd(b, a % b);} int factorial(int n, int mod) {if (n > 1)return (n * factorial(n - 1, mod)) % mod; else return 1;} int lcm(int a, int b) {return (a * b) / gcd(a, b);} vector<int> read(int n) {vector<int> a; for (int i = 0; i < n; i++) { int x; cin >> x; a.pb(x);} return a;}struct prefix_sum{vint pref;void build(vint a){pref.pb(0);for(int i = 0; i < a.size(); i++){pref.pb(pref.back()+a[i]);}}int get(int l, int r){return pref[r]-pref[l-1];}};//ssense

int get(int now)
{
	int ans = 0;
	int div = 5;
	while(div <= now)
	{
		ans+=now/div;
		div*=5;
	}
	return ans;
}

void solve()
{
	int p;
	cin >> p;
	int now = 0;
	if(p == 0)
	{
		cout << 1 << endl;
		return;
	}
	int l = 0, r = 2*p;
	while(l <= r)
	{
		int mid = l+r>>1;
		if(p <= get(mid*5))
		{
			now = mid*5;
			r = mid-1;
		}
		else
		{
			l = mid+1;
		}
	}
	cout << now << endl;
}

int32_t main(){
	startt
	int t = 1;
	freopen("fact.in", "r", stdin);
	freopen("fact.out", "w", stdout);
	//cin >> t;
	while (t--) {
		solve();
	}
}