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 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include<stdio.h>
int main()
{
	int s,c;
	int q,w;
	scanf("%d",&s);
	scanf("%d",&c);
	q=s*2;
	if(c>q)
	{
		w=c-q;
		w=w/4;
		w=w+s;
		printf("%d",w);
	}
	if(c<=q)
	{
		if(0==c%2)
		{
			w=c/2;
			printf("%d",w);
		}
		if(0!=c%2)
		{
			c--;
			w=c/2;
			printf("%d",w);
		}
	}
}