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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <iostream>
#include <algorithm>
#include <string>
#include <cstdlib>
#include <set>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <vector>
#include <map>
#include <stack>
#include <queue>
#include <cctype>
using namespace std;
int main()
{
	int n, m;
	while(scanf("%d%d", &n, &m) != EOF)
	{
		//int sum;
		int c = m / 2;
		//if(m % 2) c++;
		if(c - n > 0) 
		{
			int k = m - n * 2;
			n += k / 4;
			printf("%d\n", n);
		}
		else if(c - n == 0) printf("%d\n", n);
		else printf("%d\n", m / 2);
	}
	return 0;
}