#include <cassert>
#include <iostream>
#include <optional>
#include <string>
#include <string_view>
using namespace std;
int main() {
	int n;
	cin >> n;
	string as, bs;
	cin >> as >> bs;
	assert(as.size() == n and bs.size() == n);

	std::string_view a = as, b = bs;

	string ans;
	while(not b.empty()) {
		if(a[0] == b[0]) {
			ans.push_back(a[0]);
			a.remove_prefix(1);
			b.remove_prefix(1);
		} else {
			a.remove_prefix(1);
			if(a.size() < b.size()) swap(a, b);
		}
	}
	cout << ans << endl;
}