#include <bits/stdc++.h>
using namespace std;

int zeroes(int n){
    int res = 0;
    for(int i = 5; n / i >= 1; i *=5)
        res += n / i;
    return res;
}

int main(){
    ifstream cin("fact.in");
    ofstream cout("fact.out");
    int n, l = 1, r = 1e8, m, sol = -1;
    cin >> n;
    while(l <= r){
        m = l + (r - l) / 2;
        int ans = zeroes(m);
        if(ans >= n)
            r = m - 1;
        if(ans == n)
            sol = m;
        if(ans < n)
            l = m + 1;
    }
    cout << sol;
}