Problem:
Score : 300 points

Problem Statement

Snuke loves puzzles.

Today, he is working on a puzzle using S- and c-shaped pieces.
In this puzzle, you can combine two c-shaped pieces into one S-shaped piece, as shown in the figure below:

Snuke decided to create as many Scc groups as possible by putting together one S-shaped piece and two c-shaped pieces.

Find the maximum number of Scc groups that can be created when Snuke has N S-shaped pieces and M c-shaped pieces.

Constraints

1 ≤ N,M ≤ 10^{12}

Input

The input is given from Standard Input in the following format:

N M

Output

Print the answer.

Sample Input 1

1 6

Sample Output 1

2

Two Scc groups can be created as follows:

Combine two c-shaped pieces into one S-shaped piece

Create two Scc groups, each from one S-shaped piece and two c-shaped pieces

Sample Input 2

12345 678901

Sample Output 2

175897

Solution in C++14 (Clang 3.8.0) (judge verdict: Accepted)

#include<iostream>
using namespace std;
typedef long long LL;
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);

	LL n, m; cin >> n >> m;
	LL ans = 0;

	LL make1 = min(n,m/2);
	ans += make1;
	n -= make1;
	m -= 2*make1;

	if(m >= 2)
		ans += m/4;

	cout<<ans<<endl;
	
	cout<<flush;
	return 0;
}