#include <fstream>

using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int main()
{
    long long fact,k,x,p;
    f>>p;
    fact=256;
    k=0;
    for(x=5;x<=p*5&&k<p;x=x+5)
        {
            fact=fact*x*256;
            while(fact%10==0)
              {
                  k++;
                  fact=fact/10;
              }
        if(fact>1000000000) fact=256;
        }
       if(p==0) g<<0;
           else  if(k==p) g<<x-5;
                     else g<<-1;
       f.close();
       g.close();

    return 0;
}