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 Kotlin (1.0.0) (judge verdict: Accepted)

import java.util.Scanner
 
fun main(args : Array<String>){
  val cin = Scanner(System.`in`)
  var n = cin.nextLong()
  var m = cin.nextLong()
  var res : Long
  if (n * 2L <= m){
    res = n
    m -= n * 2L
    res += m / 4L
  }
  else res = m / 2L
  println(res)
}