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

int main() {
    int n; cin >> n;

    vector<bool> basic(n);

    vector<bool> outcome(n);
    vector<bool> diff(n);

    string cucc;

    cin >> cucc;
    for (int i = 0; i < n; i++) {
        if (cucc[i] == 'S') {
            basic[i] = true;
        } else {
            basic[i] = false;
        }
    }

    cin >> cucc;
    for (int i = 0; i < n; i++) {
        if (cucc[i] == 'S') {
            outcome[i] = true;
        } else {
            outcome[i] = false;
        }
    }

    for (int i = 0; i < n; i++) {
        if (basic[i] == outcome[i]) {
            diff[i] = false;
        } else {
            diff[i] = true;
        }
    }

    int segments = 0;

    bool inSegment = true;


    for (int i = 1; i < n; i++) {
        if (diff[i] != diff[i-1]) {
            segments++;
        }
    }

    cout << segments;
}