#include <iostream>
#include <fstream>
using namespace std;
ifstream f ("fact.in");
ofstream g ("fact.out");
int main()
{
    int n,i,c,cop;
    f>>n;
    if(n==0)
        g<<0;
    else if(n==5)
        g<<-1;
    else
    {
        c=0;
        while(n>0)
        {
            c+=5;
            cop=c;
            while(cop%5==0)
            {
                cop=cop/5;

                n--;
            }
        }
        g<<c;
    }
    return 0;
}