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.Scanner;

public class Main {
	public static void main(String args[]){
		Scanner scanner = new Scanner(System.in);
		long s = scanner.nextLong();
		long c = scanner.nextLong();
		long count = 0;
		while(true){
			//System.out.println("s="+s+" ,c="+c+" ,count="+count);
			if(s>0 && c>=2){
				long temp = Math.min(s, c/2);
				s = s-temp;
				c = c-(2*temp);
				count += temp;
			}else if(s==0 && c>=4){
				long temp = c/4;
				c = c-temp*2;
				s += temp;
			}else if(s==0 && c>2){
				c = c-2;
				s += 1;
			}else{
				break;
			}
		}
		System.out.println(count);
	}
}