#include <fstream>
 using namespace std;


 int main()
 {
     ifstream intro("fact.in");
     ofstream exit("fact.out");
     int p;
     int n;
     int z;
     int i;
     intro>>p;
     // sa mearga din 5 in 5 considerind multiplii
     n=0;z=0;
     while (z<p)
        {
            n=n+5;
            i=n;
            while (i>=1)
                     {
                         if (i%5==0) z=z+1;
                         i=i/5;

                        }

        }



      if (z!=p) n=-1;
      if (p==0) n=1;
      exit<<n;

 }