#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <iostream>
#include <map>
#include <vector>
#include <queue>
#include <set>

using namespace std;

//namaega184

int main(){ 
	int n;char s[1001],t[1001];scanf("%d%s%s",&n,s,t);
	int ans=0;for(int i=0;i<n;i++)if(s[i]!=t[i])ans++;
	printf("%d\n",ans);
	
	return 0; 
}