#include <iostream>
#include <fstream>
#include <math.h>
using namespace std;

int i,n,p,j,x;
int main()
{

    n=9999999999999999;
    x=1;
    j=1;
    ifstream f("factorial.in");
        f>>p;
    while(p>0)
    {
        x=x*10;
        p=p-1;
    }
    for(i=1;i<n;i++)
    {
        j=j*i;
        if(j%x==0)
            {
                ofstream g("factorial.out");
                g<<i;
                return 0;
            }
            else
            {
                ofstream g("factorial.out");
                g<<-1;
            }
    }
    return 0;
}