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 (Clang 3.8.0) (judge verdict: Accepted)

#include <stdio.h>

#define min(a, b) (a < b ? a : b)

int main(void) {
	long sNum = 0, cNum = 0, scc = 0;
	scanf("%ld %ld", &sNum, &cNum);
	scc += (min(sNum, cNum / 2));
	sNum -= scc;
	cNum -= scc * 2;
	scc += cNum / 4;
	printf("%ld\n", scc);
	return 0;
}