#include <iostream>
#include <fstream>

using namespace std;

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

int P , N ;

int braian_tasescu(int n)
{
    int nr=0 ;
    while (n>0)
    {
        nr+=n/5;
        n=n/5;
    }
    return nr;
}

int main()
{
    in>>P;
    int r=0 , pas=1<<28;
    while(pas!=0)
    {
        if (braian_tasescu(r+pas)<P)
        {
            r+=pas;
        }
        pas/=2;
    }
    r++;
    if (braian_tasescu(r) != P)
    {
        r = -1;
    }
    out<<r;
    return 0 ;
}