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

/*
megnézünk ilyen szegmenseket (egybefüggõ különbözõ sorozatot) és az a megoldás+1
*/

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 = false;

    if (diff[0]) {
        inSegment = true;
        segments++;
    }

    for (int i = 1; i < n; i++) {
        if (!diff[i]) {
            inSegment = false;
        } else {
            if (!inSegment) {
                inSegment = true;
                segments++;
            }
        }
    }

    cout << segments+1;
}