03. Combinations

#include <iostream>
using namespace std;

int main()
{
    int n;
    cin >> n;

    //x1, x2, x3 -> 0 до n
    int count = 0; //брой на валидни комбинации

    for (int x1 = 0; x1 <= n ; x1++)
    {
        for (int x2 = 0; x2 <= n ; x2++)
        {
            for (int x3 = 0; x3 <= n; x3++)
            {
                int sum = x1 + x2 + x3;
                if (sum == n) {
                    count++;
                }
            }
        }
    }

    cout << count << endl;
    return 0;
}