import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
sys.setrecursionlimit(10 ** 7)

n = int(readline())
s = readline().rstrip().decode()
t = readline().rstrip().decode()
print(sum(1 if ss != tt else 0 for ss, tt in zip(s, t)))