#include <fstream>
#include <iostream>

using namespace std;

int main()
{
    ifstream fin("fact.in");
    ofstream fout("fact.out");
    int p,i;
    fin>>p;
    if(p<=0)
     cout<<-1;
    else
     if(p==1)
      cout<<0;
     else
     {
      for(i=5;p!=0;i+=5)
      {
       if(i%5==0)
        p--;
       else
        if(i%10==0)
         p--;
       if(i%25==0)
        p--;
      }
     cout<<i-5;
     }
    return 0;
}