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: Wrong Answer)

        using System;
        using System.Linq;
        using static System.Math;

        public class Program
        {
            public static void Main(string[] args)
            {
            long[] input = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
            long countS = 0;
            long countC = 0;
            if (input[0] <= 2) countS = 1;
            else countS = input[1] / 2 > input[0] ? input[0] / 2 : input[1] / 2;
            countC = input[1] / 4;

            Console.WriteLine(countS + countC);
            }
        }