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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;

namespace AtCoderDiverta2019B
{
    class Program
    {
        static void Main(string[] args)
        {
            int ans = 0;

            string[] s = Console.ReadLine().Split(' ');

            int N = int.Parse(s[3]);

            int[] X = new int[3];

            for (int i = 0; i < 3; i++)
            {
                X[i] = int.Parse(s[i]);
            }

            for(int i=0;i*X[0]<=N;i++)
            {
                int rest = N - i * X[0];

                for(int j=0;j*X[1]<=rest;j++)
                {
                    int rest2 = rest - j * X[1];
                    if (rest2 % X[2] == 0)
                        ans++;
                }

            }

            Console.WriteLine(ans.ToString());
        }
    }

}