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: Runtime Error)

fun main(args:Array<String>) {
  var (n, m) = readLine()!!.split(" ").map(String::toInt)

  // n is S
  var snum = when { 
              m >= 2*n -> { 
                val ret = n
                m -= 2*n
                n = 0
                ret
              }
              else -> { 
                n = n - m/2
                val ret = m/2
                m = 0
                ret 
              }
            }
  //println("$snum $n $m")
  val sofm = m / 4 
  
  snum += sofm
  println(snum)
}