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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		try {
			int k = sc.nextInt();
			int s = sc.nextInt();

			int ans = 0;
			for (int a = 0; a <= k; a++) {
				if (a == s) {
					ans++;
					break;
				}
				int bc  = (int) Math.ceil((double) (s - a) / 2);
				if (bc <= k) {
					for (int b = 0; b <= k; b++) {
						if (s - a - b >= 0 && s - a - b <= k) {
							ans++;
						}
					}
				}
			}

			System.out.println(ans);

		} finally {
			sc.close();
		}
	}
}