#include <fstream.h>
#include <iostream.h>
int main()
{
   ifstream fin("fact.in");
   ofstream fout("fact.out");
   int n=0,b,ct=0,p;
   fin>>p;
   while (ct<p)
   {
    n=n+1;
    if (!(n%5)) ct=ct+1;
    ct=ct+1;
   }
   n=n*5;
   if (p==0) n=1;
   fout<<n;
   return 0;
}