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;
using System.IO;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Numerics;
using System.Threading.Tasks;
using System.Text.RegularExpressions;
using Debug = System.Diagnostics.Debug;
using System.Runtime.CompilerServices;
using static System.Math;
using MethodImplOptions = System.Runtime.CompilerServices.MethodImplOptions;
using MethodImplAttribute = System.Runtime.CompilerServices.MethodImplAttribute;

static class P
{
    static void Main()
    {
        var rgbn = Console.ReadLine().Split().Select(int.Parse).ToArray();
        var r = rgbn[0];
        var g = rgbn[1];
        var b = rgbn[2];
        var n = rgbn[3];
        int res = 0;
        for (int i = 0; i * r <= n; i++)
        {
            for (int j = 0; i * r + j * g <= n; j++)
            {
                if ((n - (i * r + j * g)) % b == 0)
                {
                    //Console.WriteLine($"{i} {j} {(n - (i * r + j * g)) / b}");
                    res++;
                }
            }
        }
        Console.WriteLine(res);
    }
}