#include<stdio.h>

   int main()
{
    long i, j, k, f=0, n, p, st, dr, mj;

     freopen("fact.in", "r", stdin);
     freopen("fact.out", "w", stdout);

    scanf("%ld", &p);

 st=1;
 dr=p*5;

   while(st!=dr)
   {
     mj=(st+dr)/2; f=0;
       for(i=1;i<=mj;i++)
        {   k=i;
               while(k%5==0)
                { f++; k=k/5; }
        }
       if(f<p)
        st=mj+1;
         else
        dr=mj;
   }
  printf("%ld", st);

return 0;

}