def make_negative(number):
if number > 0:
i = f"-{number}"
print(int(i))
elif number < 0:
print(number)
else:
print(0)
f = make_negative(10)
e = make_negative(20)
print(f + e)
-10 -20 Traceback (most recent call last): File "C:/Python/Цикл.py", line 12, in <module> print(f + e) TypeError: unsupported operand type(s) for +: 'NoneType' and 'NoneType'