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

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

    string s, t;
    cin >> s >> t;

    int steps = 0;
    bool flipped = false;

    for (int i = n - 1; i >= 0; i--) {
        char cur = s[i];
        if (flipped) {
            cur = (cur == 'S' ? 'F' : 'S');
        }

        if (cur != t[i]) {

            steps++;
            flipped = !flipped;
        }
    }

    cout << steps;
    return 0;
}