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: Wrong Answer)

#include <bits/stdc++.h>

using namespace std;

int main() {
  int K, S, ans = 0;
  
  cin >> K >> S;
  
  vector<int> lk;
  
  for (int j = 0; j <= K; j++) {
  for (int k = 0; k <= K; k++) {
    lk.push_back(S - k - j);
  }
  }
  
  sort(lk.begin(), lk.end());
  
  for (int i = 0; i <= K; i++) {
    if (*lower_bound(lk.begin(), lk.end(), i) - i == 0) {
      ans++;
    }
  }
  
  cout << ans << endl;
  
  return 0;
}