#include<fstream.h>
int main()
{
  long k,p,i,m;
  ifstream f("fact.in");
  ofstream g("fact.out");
  f>>p;
  k=0;
  i=0;
  while (k<p)
    { i+=5;;
      m=i;
      while (m%5==0){ m=m/5; k++;}}
  if (k==0) g<<"1";
   else g<<i; 
  f.close();
  g.close(); }