Hey, Just like programmers prepare notebook for contests like icpc, has anyone prepared interview prep notebook for last min revisions ?

We are given an array of size N, we can delete a subset b1b2b3...bk from the array if 2^b1 + 2^b2 + …..2^bk = 2^x for non-negative integer x where ^ is the power operator. Find the minimum number of steps required to delete the complete array.

0 <= ai <= 1000000

1 <= N <= 1000000