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# (Mono-csc 3.5.0) (judge verdict: Wrong Answer)


using System;
using System.Collections.Generic;
using System.Linq;
class Test
{

    public static void Main()
    {
        var inp = Console.ReadLine().Split(' ').Select(x => long.Parse(x)).ToArray();

        long n = inp[0];
        long k = inp[1];
        if (k < 2)
        {
            Console.Write(0);
        }
        if (n * 2 <= k)
        {
            Console.Write(n + (k - n * 2) / 4);
        }
        if (n >= k)
        {
            Console.Write(k / 2);
        }

    }


}