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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;

namespace AtCoder
{
    class B_SumofThreeIntegers_051
    {
        public static void Main()
        {
            string[] input = Console.ReadLine().Split(' ');
            var S = int.Parse(input[0]);
            var K = int.Parse(input[1]);

            var count = 0;
            for (var x = 0; x <= K; ++x)
            {
                for (var y = 0; y <= K; ++y)
                {
                    for (var z = 0; z <= K; ++z)
                    {
                        if (x + y + z == S) { ++count; }
                    }
                }
            }

            Console.WriteLine(count);
        }
    }
}