#include<stdio.h>
int main(){
  unsigned long int N;
  unsigned long int a,b,c;
  unsigned long int ans;
  scanf("%lu",&N);
  a=N/3;b=N/3;c=N/3;
  ans = ((a-c)+(b-3)+c*2)*2;
  printf("%lu",ans);
  return 0;
}