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 JavaScript (node.js v5.12) (judge verdict: Accepted)

function Main(input) {
  s=input.split(" ")[0];
  c=input.split(" ")[1];
  if(c>=s*2){
  c=c-2*s;
  a=s;
  s=0;
  b=Math.floor(c/4);
  }else{
  a=0;b=Math.floor(c/2);}
 
console.log(Number(a)+Number(b));
}
 
Main(require("fs").readFileSync("/dev/stdin", "utf8"));