#include <bits/stdc++.h>
using namespace std;
#define endl '\n'

ifstream in ("fact.in");
ofstream out ("fact.out");

int check (int x) {
    int a = 5, ans = 0;
    while(x >= a) {
        ans += x / a;
        a = a * 5;
    }
    return ans;
}

int main() {
    int n;
    in >> n;
    int st  = 1, dr = INT_MAX - 1, ans = INT_MAX;
    while(st <= dr) {
        int m = (st + dr) / 2;
        if(check(m) < n) st = m + 1;
        else {
            dr = m - 1; 
            ans = m;
        }
        
    }

    if( check(ans) == n) out << ans;
    else out << "-1";
}