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 (1.15.1) (judge verdict: Accepted)

fn run() {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    let mut it = s.trim().split_whitespace();
    let r: usize = it.next().unwrap().parse().unwrap();
    let g: usize = it.next().unwrap().parse().unwrap();
    let b: usize = it.next().unwrap().parse().unwrap();
    let n: usize = it.next().unwrap().parse().unwrap();
    let mut ans = 0;
    for i in (0..).filter(|&x| x % r == 0).take_while(|&x| x <= n) {
        for j in (0..).filter(|&x| x % g == 0).take_while(|&x| x <= n - i) {
            let k = n - i - j;
            if k % b == 0 {
                ans += 1;
            }
        }
    }
    println!("{}", ans);
}

fn main() {
    run();
}