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

long long k=0,n,p,aux;

int main()
{
    f>>p;
    for(n=5;k<p;n+=5)
    {
        aux=n;
        while(aux%5==0)
        {
            aux/=5;
            k++;
        }
    }
    if(n==5)
        g<<1;
    else if(k>p)
            g<<-1;
        else
            g<<n-5;


    return 0;
}