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Contest: Task: Related: TaskB

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:

9b0bd546db9f28b4093d417b8f274124.png

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