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

	string ans;
	for(int i = 0; i < n; ++i)
		if(a[i] == b[i]) ans.push_back(a[i]);
	cout << ans << endl;
}