#include <algorithm>
#include <cstdio>
#include <iostream>
#include <map>
#include <cmath>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <stdlib.h>
#include <stdio.h>
#include <bitset>
using namespace std;
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
typedef long long ll;

int main()
{
  int n;
  cin >> n;
  string s, t;
  cin >> s >> t;
  int cnt = 0;
  FOR(i,0,n) {
    if(s[i]!=t[i]) cnt++;
  }
  cout << cnt << endl;
  return 0;
}