#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

void solve(){
  
  int n ; cin>>n;
  string s1, s2; cin>>s1>>s2;
  
  int count = 0;
  
  for(int i = 0; i < n; i++){
    if(s1[i] != s2[i]) count++;
  }
  
  cout<<count<<endl;
  
  
}


int main() 
{
    solve();
    return 0;
}