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

using pint = pair< int, int >;
using ull = unsigned long long;

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