#include <fstream>
#include <iostream>

using namespace std;

int main()
{
    long p, pow, zeros, i, no;

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

    fin>>p;
    fin.close();

    for(i = 0, zeros = 0, pow = 1, no = 5; zeros <= p; i += 5)
    {
        if(i == no)
        {
            zeros += pow;
            no *= 5;
            ++pow;
        }
        else
            ++zeros;
    }
    if(zeros == p)
        fout<<i;
    else
        fout<< -1;

    fout.close();
    return 0;
}