#include <iostream>
#include <fstream>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int nrzero(int n)
{
    int nr = 0;
    for (int i = 5; i <= n; i = i * 5)
    {
        nr = nr + n / i;
    }
    return nr;
}
int main()
{
    int n, p;
    in >> p;
    int st = 1, dr = 2000000000, c, mij;
    bool ok = 0;
    while (st <= dr && ok == 0)
    {
        mij = (st + dr) / 2;
        int x = nrzero(mij);
        if (x == p)
        {
            c = mij;
            ok = 1;
        }

        else if (x < p)
            st = mij + 1;
        else
            dr = mij - 1;
    }
    if (ok == 0)
        out << -1;
    else if (c - c % 5 != 0)
        out << c - c % 5;
    else out << 1;
    return 0;
}