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)

use std::io::Read;

fn main() {
    let mut buf = String::new();
    std::io::stdin().read_to_string(&mut buf).unwrap();

    let answer = solve(&buf);

    println!("{}", answer);
}

fn solve(input: &str) -> String {
    let mut iterator = input.split_whitespace();

    let r: isize = iterator.next().unwrap().parse().unwrap();
    let g: isize = iterator.next().unwrap().parse().unwrap();
    let b: isize = iterator.next().unwrap().parse().unwrap();
    let n: isize = iterator.next().unwrap().parse().unwrap();

    let mut ans = 0;
    for i in 0..(n / r + 1) {
        for j in 0..(n / g + 1) {
            let k1 = (n - i * r - j * g) / b;
            let k2 = (n - i * r - j * g) % b;
            if k1 >= 0 && k2 == 0 {
                ans += 1;
            }
        }
    }

    return ans.to_string();
}