def solution(concentrations, target):
    answer = 0

    def dfs(start, cnt, total):
        nonlocal answer

        if cnt == 4:
            if total == target:
                answer += 1
            return

        for i in range(start, len(concentrations)):
            dfs(i + 1, cnt + 1, total + concentrations[i])

    dfs(0, 0, 0)

    return answer

concentrations = [20, 20, 20, 20, 40, 40, 40, 40]
target = 120

print(solution(concentrations, target))