#define _USE_MATH_DEFINES

#include <iostream>
#include <iomanip>

#include <algorithm>
#include <cmath>

#include <string>
#include <list>
#include <queue>
#include <vector>
#include <complex>

/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define P(p) std::cout<<(p)<<std::endl;
/////////
typedef long long LL;
typedef long double LD;
/////////
using namespace::std;
/////////

int main(void){
    std::cin.tie(0);
    std::ios::sync_with_stdio(false);
    std::cout << std::fixed;//
    //cout << setprecision(6);//
	
	int N;
	string S,T;
	cin>>N>>S>>T;
	int ans = 0;
	rep(i,S.size()){
		if(S[i] != T[i]){
			++ans;
		}
	}
	P(ans);
	return 0;
}