#include<bits/stdc++.h>
using namespace std;
using Int = long long;
//INSERT ABOVE HERE
signed main(){
  Int n;
  cin>>n;
  string s,t;
  cin>>s>>t;
  Int ans=0;
  for(Int i=0;i<n;i++) ans+=s[i]!=t[i];
  cout<<ans<<endl;
  return 0;
}