Problem:
Score : 200 points

Problem Statement

Snuke has come to a store that sells boxes containing balls. The store sells the following three kinds of boxes:

Red boxes, each containing R red balls

Green boxes, each containing G green balls

Blue boxes, each containing B blue balls

Snuke wants to get a total of exactly N balls by buying r red boxes, g green boxes and b blue boxes.
How many triples of non-negative integers (r,g,b) achieve this?

Constraints

All values in input are integers.

1 \leq R,G,B,N \leq 3000

Input

Input is given from Standard Input in the following format:

R G B N

Output

Print the answer.

Sample Input 1

1 2 3 4

Sample Output 1

4

Four triples achieve the objective, as follows:

(4,0,0)

(2,1,0)

(1,0,1)

(0,2,0)

Sample Input 2

13 1 4 3000

Sample Output 2

87058

Solution in Rust (1.42.0) (judge verdict: Accepted)

fn main() {
    let mut input: String = String::new();
    let stdin = std::io::stdin();
    let _ = stdin.read_line(&mut input);
    let rgbn = input
        .trim()
        .split_whitespace()
        .map(|n| n.parse().expect("parse"))
        .collect::<Vec<u32>>();
    println!("{}", solve(rgbn[0], rgbn[1], rgbn[2], rgbn[3]));
}

fn solve(r: u32, g: u32, b: u32, n: u32) -> u32 {
    // no brain
    let mut ans = 0;
    for buy_r in 0..=(n / r) {
        for buy_g in 0..=((n - r * buy_r) / g) {
            if (n - r * buy_r - g * buy_g) % b == 0 {
                ans += 1;
            }
        }
    }
    ans
}