Find the complement of a number

[landlord1984]

I want to find the complement of a number
For example:

The binary representation of 5 is 101 (no leading zero bits), and its complement is 010. So you need to output 2.
The binary representation of 1 is 1 (no leading zero bits), and its complement is 0. So you need to output 0.

From: https://www.tutorialspoint.com/python/bi...xample.htm
It suggests it just need to use "~". It shows:

a=60

bin(a)=0011 1100 
bin(~a)= 1100 0011=-61

But on my python3.5, what I get is:

a=60
bin(a)=0011 1100 
bin(~a)= 111101=-61

The resulted number -61 is right, but its binary form is not complement of a.

What happened?

Thanks,

L