#include <iostream>
#include <string>
#include <vector>

using namespace std;
int main() {
	int n;
	string a, b;
	cin >> n >> a >> b;
	vector<int> d(n + 1, 0);

	for(int i = 0; i < n; ++i) {
		int m    = 0;
		int last = 0;
		for(int j = 0; j < n; ++j) {
			auto t = max({m, d[j + 1], last + (a[i] == b[j])});
			last   = d[j + 1];
			m = d[j + 1] = t;
		}
	}
	// This gives a wrong answer currently, but it will TLE before that time anyway.
	cout << d.back() << endl;
}