#include <bits/stdc++.h>
using namespace std;
#define x1 "factorial.in"
#define x2 "factorial.out"
ifstream in(x1);
ofstream out(x2);
int zero(int nr) {
    int ans = 0, p5 = 5;
    while(p5 <= nr){
        ans += nr / p5;
        p5 *= 5;
    }
    return ans;
}
int main() {
    int n, r = 0, pas = 1 << 30;
    in >> n;
    while(pas) {
        if(zero(pas + r) < n)
            r += pas;
        pas /= 2;
    }
    if(zero(r + 1) == n)
        out << r + 1;
    else
        out << -1;
    return 0;
}