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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.Scanner;
import java.util.ArrayList;
import java.util.HashSet;
import java.lang.Integer;
import java.lang.StringBuilder;
import java.lang.Math;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long N = in.nextLong();
        long M = in.nextLong();
        long result = 0;

        if (N == 0 && M == 0) {
            result = 0;
        } else if (N >= M / 2) {
            result = M / 2;
            N -= M / 2;
            result += N / 3;
        } else {
            result = N;
            M -= 2 * N;
            result += M / 4;
        }

        System.out.println(result);
    }
}