#include <fstream>
using namespace std;

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

int zero(int n) {
    int rez = 0, p = 5;
    while (p <= n) {
        rez += n/p;
        n /= p;
    }
    return rez;
}

int caut(int p) {
    int i = 0, pas = 1<<29;
    while (pas != 0) {
        if (zero(i + pas) < p)
            i += pas;
        pas /= 2;
    }
    return i + 1;
}

int main()
{
    int x, r;
    in >> x;
    r = caut(x);
    if (zero(r) == x)
        out << r;
    else out << -1;

    return 0;
}