CodeForces 669A Little Artem and Presents

题意：同学有n个糖果，然后每一次可以给人任意个糖果，但是给出去的糖果数量得保证和上一次的数量不一样。问你最多能给多少手

思路：显然是1 2 1 2 1 2这样的...

#include<bits/stdc++.h>
using namespace std;

int main()
{
     int n;
	 scanf("%d",&n);
	 printf("%d\n",(n/3)*2+((n%3)?1:0));
}

Description

Little Artem got n stones on his birthday and now wants to give some of them to Masha. He knows that Masha cares more about the fact of receiving the present, rather than the value of that present, so he wants to give her stones as many times as possible. However, Masha remembers the last present she received, so Artem can't give her the same number of stones twice in a row. For example, he can give her3 stones, then 1 stone, then again 3 stones, but he can't give her 3 stones and then again 3 stones right after that.

How many times can Artem give presents to Masha?

Input

The only line of the input contains a single integer n (1 ≤ n ≤ 10⁹) — number of stones Artem received on his birthday.

Output

Print the maximum possible number of times Artem can give presents to Masha.

Sample Input

Input

1

Output

1

Input

2

Output

1

Input

3

Output

2

Input

4

Output

3