#include<iostream>
#include<fstream>
ifstream in("fact.in");
ofstream out("fact.out");
using namespace std;

int powerOf5(int n)
{
    int c = 0, i;
    for (i = 5; i <= n; i *= 5)
        c += n/i;

    return c;
}

int main()
{
    int p, st = 1, dr = 1000000000, m;
    in >> p;

    if (p==0) out << 1;
    else
        {
        while (st <= dr)
        {
            m = (st + dr) / 2;
            if (powerOf5(m) < p)
                st = m + 1;
            else
                dr = m - 1;
        }


    if (powerOf5(st) == p)
        out << st;
    else
        out << -1;
        }
    return 0;
}