#include <iostream>
#include <fstream>

using namespace std;

int main () {

     int p, fact = 1, putere = 1, n = 5;
     bool gasit = false;

     ifstream in ("fact.in");
     in >> p;
     in.close();

     for (int i = 1; i <= p; i++) {
          putere *= 5;
     }

     do {

          if (p == 0) {
               ofstream out ("fact.out");
               out << 1;
               out.close();
	       gasit = true;    
          } else if (fact % putere == 0) {
               if (fact % (putere * 5) == 0) {
                    ofstream out ("fact.out");
                    out << -1;
                    out.close(); 
               } else {
                    ofstream out ("fact.out");
                    out << n - 5;
                    out.close();
               }
               gasit = true;
          }
          fact *= n; 
          n += 5;
     } while (!gasit);

     return 0;
}