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

int main() {
	int n;
	string s, t;
	cin >> n >> s >> t;
	int i = 0, j = n - 1, moves = 0;
	bool turn = false;
	while (true) {
		bool out = false;
		/*while ((s[i] == t[i]) ^ turn) {
			i++;
			if (i > j) {
				out = true;
				break;
			}
		}*/

		if (out) break;
		while ((s[j] == t[j]) ^ turn) {
			j--;
			if (i > j) {
				out = true;
				break;
			}
		}

		if (out) break;
		moves++;
		turn = !turn;
	}

	cout << moves;
}