#include <array>
#include <cassert>
#include <cstddef>
#include <iostream>

int main()
{
    const std::array<int, 4> a{8, 4, 2, 1};
    std::size_t inversions = 0;
    for (std::size_t i = 0; i < a.size(); ++i) {
        for (std::size_t j = i + 1; j < a.size(); ++j) {
            if (a[i] > a[j]) {
                ++inversions;
            }
        }
    }
    assert(inversions == 6);
    std::cout << "Inversions: " << inversions << '\n';
}