#include <iostream>
#include <fstream>

using namespace std;




int main()
{
    ifstream be("factorial.in");
    ofstream ki("factorial.out");
    int p, i=0;
    be>>p;
    int k=p;
    if(k==0)ki<<1;
    else
    if((p+1)%6==0)
        ki<<-1;
    else{
    while(p>5){
        p/=5;
        i++;
    }
    ki<<(k*5)-(i*5);
    }
    return 0;
}