#include <iostream>

using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");


int numaraZerouri(int n) {
    int k = 5, zerouri = 0;
    while(k <= n) {
        zerouri += n / k;
        k *= 5;
    }
    return zerouri;
}

int main() {
    int p, n;
    bool cauta = true;
    in >> p;

    if(p == 0)
        out << 1;
    else
    {
        n = 1;
        while(cauta) {
            if(numaraZerouri(n) >= p) {
                cauta = false;
            } else {
                n++;
            }
        }

        out << ((numaraZerouri(n) == p) ? n : -1);
    }

    return 0;
}