#include <fstream>

using namespace std;
int p5 (int n)
{
    int pu5 = 0;
    while (n >= 5){
        pu5 += n / 5;
        n /= 5;
    }
    return pu5;
}
int main()
{
    ifstream in("fact.in");
    ofstream out("fact.out");
    int p, nr5, r, pas;
    in >> p;
    nr5 = 0;
    pas = 1 << 29;
    r = 0;
    while (pas != 0)
    {
        if (p5 (r + pas) < p)
        {
            r += pas;
        }
        pas /= 2;
    }
    r++;
    if (p5(r) == p)
        out << r;
    else
        out << -1;
    return 0;
}