Goal
You have a number N of magic stones each of which has a level with a positive integer value.
The stones are very heavy and cumbersome to carry around.
Luckily you can use your magic powers to combine two stones of level i to form a single stone of level i+1.
Use your power to minimise the number of stones that you have.
Input
Line 1: An integer N for the number of magic stones you have.
Line 2: N space separated integer values
Output
Line 1: The minimum number of stones you can have.
