C. Spooky Hallway
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

On Halloween night, you find yourself in a spooky hallway lined with lanterns. Each lantern is either on (represented by '1') or off (represented by '0'). However, to escape the haunted hallway, all the lanterns need to be either on or off. You have a magical ability: you can flip all the lanterns in any one contiguous section of the hallway, turning all the '1's to '0's and all the '0's to '1's.

You want to get out of the hallway as fast as possible, so you want to make all the lanterns either on or off with the fewest number of lantern flips.

Input

The first line contains an integer $$$n$$$ $$$(1 \leq n \leq 10^5)$$$, the number of lanterns in the hallway.

The second line contains a binary string $$$S$$$ of length $$$n$$$, where each character represents the state of a lantern ('1' for on and '0' for off).

Output

Print the minimum number of lantern flips you need to do to make all the lanterns either on or off.

Example
Input
10
1001011001
Output
3