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;
using System.Linq;

namespace AtCoder_Beginner_Contest_051_B
{
    class Program
    {
        static void Main(string[] args)
        {
            int[] kj = Console.ReadLine().Split().Select(int.Parse).ToArray();
            int K = kj[0], S = kj[1];
            int answer=0;
            for (int i = 0; i <= K; i++)
            {
                if (i <= K)
                {
                    for (int k = 0; k <= S-i;k++)
                    {
                        if (k<=K)
                        {
                            answer++;
                        }
                    }
                }
            }
            Console.WriteLine(answer);
            Console.ReadLine();
        }
    }
}