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

int main() {
    int n;
    cin >> n;
    vector<bool> a(n), b(n);
    char c;
    for (int i = 0; i < n; i++) {
        cin >> c;
        a[i] = c == 'S';
    }
    for (int i = 0; i < n; i++) {
        cin >> c;
        b[i] = c == 'S';
    }
    bool same = 1;
    int r = 0;
    for (int i = n - 1; i >= 0; i--) {
        if ((a[i] == b[i]) != same) {
            r++;
            same = !same;
        }
    }
    cout << r;
}