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++14 (GCC 5.4.1) (judge verdict: Time Limit Exceeded)

#include <iostream>
#include <math.h>
#include <string>
#include <vector>
#include <algorithm>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define INF 1000000;

using ll = long long;
using namespace std;

int main(){
    int k, s,all_sum, count=0;
    cin >> k >> s;
    rep(i, k+1){
        rep(j, k+1){
            rep(l, k+1){
                all_sum = i+j+l;
                if(all_sum==s) count++;
            }
        }
    }
    cout << count << endl;
}