#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");

int zeros(int n)
{
    int v=0, c=5;
    while(c<=n)
    {
        v=v+n/c;
        c=c*5;
    }
    return v;
}

int main()
{
    int p, st=1, dr=400000015, m, n;
    f>>p;
    while(st<=dr)
    {
        m=(st+dr)/2;
        if(zeros(m)>=p)
        {
            dr=m-1;
            n=m;
        }
        else
            st=m+1;
    }
    if(zeros(n)==p)
        g<<n;
    else
        g<<"-1";
    return 0;
}