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: Accepted)

using static System.Console;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var str = ReadLine().Split().Select(x=>int.Parse(x)).ToArray();
        int k = str[0], s = str[1];
        var cnt = 0;
        for(var x = k;x>=0;x--)
        {
            for(var y = k; y >= 0; y--)
            {
                var z = s - x - y;
                if (z >= 0 && z <= k) cnt++;
            }
        }
        WriteLine(cnt);                    
    }
}