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: Accepted)

import java.util.*;
public class Main {
  public static void main(String[] args) {
     Scanner sc = new Scanner(System.in);
      long N = sc.nextLong();
      long M = sc.nextLong();
      long result = 0;
      //if (M >= 2) {
        if (N*2 <= M) {
          if ((M - N*2) >= 4) {
            result = ((M - N*2) / 4) + N;
          } else {
            result = N;
          }
        } else {
          result = M/2;
        }
        //} else {
        //result = 0;
        //}
      System.out.println(result);
  }
}