def main():
	import sys

	data = sys.stdin.read().strip().splitlines()
	if len(data) < 3:
		return

	n = int(data[0].strip())
	s = data[1].strip()
	t = data[2].strip()


	diff = sum(1 for a, b in zip(s, t) if a != b)

	print(diff)


if __name__ == "__main__":
	main()