#include<stdio.h>
long int i,n,div,nr;
int main()
{
 FILE *in=fopen("fact.in","rt");
 fscanf(in,"%ld",&n);
 fclose(in);
 for(i=5;div<=n;i+=5)
 {
  nr=i;
  if(nr%25==0)
  while(nr%25==0) {div+=2;nr=nr/25;}
  else div++;
 }
  FILE *out=fopen("fact.out","wt");
  if(n==0)
  fprintf(out,"1");
  else
  fprintf(out,"%ld",i-10);
  fclose(out);
 

 return 0;
}