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 PyPy3 (7.3.0) (judge verdict: Time Limit Exceeded)

def main():
    N,M = [int(x) for x in input().split()]
    Scc_cnt = 0
    while N >= 0 and M >= 2:
        if N >= 1 and M >= 2:
            N -= 1
            M -= 2
            Scc_cnt += 1
        if N == 0 and M >= 4:
            M -= 4
            Scc_cnt += 1
        if N == 0 and M <= 3:
            break
    print(Scc_cnt)

if __name__ == '__main__':
    main()