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 4.6.2.0) (judge verdict: Runtime Error)

class Program
{
    static void Main(string[] args)
    {
        string line = System.Console.ReadLine().Trim();

        string[] Data = line.Split(' ');
        int N = int.Parse(Data[0]);
        int M = int.Parse(Data[1]);

        int count = 0;

        while (true)
        {
            N -= 1;
            M -= 2;

            if(M<0)
            {
                break;
            }

            if(N <0)
            {
                if(M>=2)
                {
                    N++;
                    M -=2;
                }
                else
                {
                    break;
                }
            }
            
            count++;
        }


        System.Console.WriteLine(count);
    }
}