#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> VI;
typedef vector<VI> VVI;
#define REP(i, n)           for(int(i)=0;(i)<(n);++(i))
#define FOR(i, f, t)        for(int(i)=(f);(i)<(t);(++i))
#define RREP(i, n)          for(int(i)=(n)-1;(i)>=0;--(i))
const int MOD = int(1e9+7);

int main(){
    int n;
    string s, t;
    cin >> n >> s >> t;

    int res = 0;
    REP(i,n) if(s[i]!=t[i]) res++;

    cout << res << endl;
    return 0;
}