def teil_b(res1):
    global result
    result = 0
    return res1
result = 0
def rec(integer):
    global result
    if integer == 0:
        integer = 0
        return teil_b(result)
    else:
        print("vorher:", result)
        result = result + integer * integer
        print("nachher:", result)
        return rec(integer-1)

assert itr(2) == rec(2)