Bulbs

2×N bulbs are arranged in two rows. Each row has N bulbs, and initially every bulb is off.

Hyunsu wants to create a desired beautiful pattern in several operations. In one operation, he chooses one or more consecutive bulbs in a single row or a single column, then toggles all chosen bulbs. An off bulb becomes on, and an on bulb becomes off.

Given the target pattern, determine the minimum number of operations needed to create it.

The first line contains the number of columns N. (1 ≤ N ≤ 10,000)

The next two lines describe the pattern Hyunsu wants to create. 1 means the bulb is on, and 0 means the bulb is off.

Output the minimum number of operations needed to create the desired pattern.