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 Rust (1.15.1) (judge verdict: Time Limit Exceeded)

use std::io::{stdin, stdout, BufReader, BufWriter, Read, Write};

pub fn solve<R: Read, W: Write>(input: R, output: W) {
    let mut reader = BufReader::new(input);
    let mut writer = BufWriter::new(output);

    let mut buf = String::new();
    reader.read_to_string(&mut buf).unwrap();
    let mut v = buf.split_whitespace().map(|s| s.parse::<i32>().unwrap());
    let k = v.next().unwrap();
    let s = v.next().unwrap();

    let mut cnt = 0;
    for x in 0..(k + 1) {
        for y in 0..(k + 1) {
            for z in 0..(k + 1) {
                if x + y + z == s {
                    cnt += 1;
                }
            }
        }
    }

    writer.write(cnt.to_string().as_bytes()).unwrap();
    writer.write(b"\n").unwrap();
}

fn main() {
    solve(stdin(), stdout());
}