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: Time Limit Exceeded)

#define _USE_MATH_DEFINES
#include <iostream>
#include <numeric>
#include <string>
#include <vector>
#include <algorithm>
#include <sstream>
#include <iterator>
#include <math.h>
#include <cmath>
#include <set>   

using namespace std;


int main() {
	long long n, m;
	long long count = 0;
	cin >> n >> m;

	for (long long i = 0; i < 10000000000; i++)
	{
		if (n >= 1 && m >= 2) {
			count++;
			n -= 1;
			m -= 2;
			continue;
		}

		if (m >= 4) {
			count++;
			m -= 4;
			continue;
		}

		break;
	}
	
	cout << count << endl;
	return 0;
				
}