Почему выдает ошибку?
" File "main.py", line 21
result_a = a*ai+1
^
IndentationError: expected an indented block

ВОТ КОД НА ПИТОНЕ
a = int(input())

b = int(input())

ai = 1

bi = 1

alist = []

for i in range(2000):

result_a = a*ai+1

alist.append(result_a)

ai = ai + 1

for i in range(2000):

result_b = b*bi-1

if result_b in alist:

 print(result_b)

 break

bi = bi + 1