#include <fstream>

using namespace std;

int main()
{
    ifstream fin("fact.in");
    ofstream fout("fact.out");
 int P,zerouri=0, N=1,crescator=2,N1=1;
 fin >>P;
 if(P>=0) {
  while( zerouri<=P && P!=zerouri){
    N1=N1*crescator;
    N=N+1;
    while(N1%10==0)
    {
        ++zerouri;
        N1/=10;
    }
   while(N1>100)
       N1=(N1%100);
    ++crescator;
  }
  if(zerouri!=P)
  fout << "-1";
  else
  fout <<N;}
 else
    fout << "-1";
  return 0;
}