# t = int(input())
# n = int(input())
# a = list(map(int,input().split()))
# a,b,c = map(int,input().split())
# s = list(input())
#By Tahir Huzaifa on 3/01/2026

import math
from collections import Counter
from collections import defaultdict
n = int(input())
s = list(input())
t = list(input())
cnt=0

for i in range(n):
    if s[i]!=t[i]:
        cnt+=1
print(cnt)