Problem:
Score : 200 points

Problem Statement

You are given two integers K and S.

Three variable X, Y and Z takes integer values satisfying 0≤X,Y,Z≤K.

How many different assignments of values to X, Y and Z are there such that X + Y + Z = S?

Constraints

2≤K≤2500

0≤S≤3K

K and S are integers.

Input

The input is given from Standard Input in the following format:

K S

Output

Print the number of the triples of X, Y and Z that satisfy the condition.

Sample Input 1

2 2

Sample Output 1

6

There are six triples of X, Y and Z that satisfy the condition:

X = 0, Y = 0, Z = 2

X = 0, Y = 2, Z = 0

X = 2, Y = 0, Z = 0

X = 0, Y = 1, Z = 1

X = 1, Y = 0, Z = 1

X = 1, Y = 1, Z = 0

Sample Input 2

5 15

Sample Output 2

1

The maximum value of X + Y + Z is 15, achieved by one triple of X, Y and Z.

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

function Main(input) {
    input = input.split("\n");
    var line = input[0].split(" ");
    var K = parseInt(line[0]);
    var S = parseInt(line[1]);
    var roop = Math.min(K,S);
    var ans =0;
    for(var A=0;A<=roop;A++){
        if(S-K-A>=0){
            if(2*K-S+A+1>0){
                ans += 2*K-S+A+1;
            }
        }
        else if(S-K-A<0){
            if(S-A+1>0){
                ans += S-A+1;
            }
        }
    }
    console.log(ans);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));