#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    unsigned long p, i, zero = 0, b = 100000, ok = 0, ci;

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

    in>>p;

    for(i=1; i<b; i++)
    {
        if (i%5 == 0)
        {
            ci = i;
            while (ci%5 == 0)
            {
                zero ++;
                ci = ci/5;
            }

            if (p == zero)
            {
                out<<i;
                ok = 1;
                break;
            }
        }
    }

    if (ok == 0)
        out<<"-1";


    return 0;
}