def solution(a, b): # O(1)

"""

Calculate the sum of two integers a and b,

but you are not allowed to use the operator + and -.

>>> solution(2, 3)

5

"""

while b != 0: # O(1)

# carry now contains common set bits of a and b

carry = a & b # O(1)

# Sum of bits of a and b where at east one of the bits is not set

a = a ^ b # O(1)

# Carry is shifted by one so that adding it to b gives the required sum

b = carry << 1 # O(1)

return a # O(1)

if __name__ == '__main__':

import doctest

doctest.testmod()