#coding: UTF-8

import sys
import re
import itertools
from collections import deque

### defs ###

### main ###
n = int(sys.stdin.readline())
S = sys.stdin.readline().strip('\n')
T = sys.stdin.readline().strip('\n')

ans=0
for s,t in zip(S,T):
	if(s!=t):
		ans += 1
print(ans)