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 Go (1.6) (judge verdict: Accepted)


package main

import (
  "fmt"
)


func get() (int, int) {
  var n, m int
  fmt.Scan(&n)
  fmt.Scan(&m)
  return n, m
}


func main() {
  n, m := get()
  if n < m {
    a := n + ((m - (n * 2)) / 4)
    fmt.Println(a)
  } else {
    a := (m / 2)
    fmt.Println(a)
  }
}