#include <iostream>
#include <iomanip>
#include <sstream>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <list>
#include <set>
#include <algorithm>
#include <utility>
#include <functional>
#include <numeric>
#include <cassert>
#include <cmath>
#include <string>
#include <cctype>
#include <cstdio>
#include <cstdlib>

using namespace std;

#define DEBUGGING 1

#if defined(DEBUGGING)
#define debug(...) fprintf(stderr,__VA_ARGS__)
#else
#define debug(...)
#endif

int main()
{
	int n;
	string a,b;
	cin >> n;
	cin >> a >> b;

	int n2 = (n+1)/2;

	string s;
	int i=0,j=0;

	while ( (int)s.length()<n2 ) {
		if ( max(i,j)>=n ) break;
		vector<int> a_has(26,-1), b_has(26,-1);

		bool added = false;
		for(int i1=i, j1=j; max(i1,j1)<n; ) {

			if ( a_has[a[i1]-'A']<0 ) a_has[a[i1]-'A'] = i1;
			if ( b_has[b[j1]-'A']<0 ) b_has[b[j1]-'A'] = j1;

			if ( b_has[a[i1]-'A']>=0 ) {
				s += a[i1];
				j = b_has[a[i1]-'A']+1;
				i = i1+1;
				added = true;
				break;
			}
			if ( a_has[b[j1]-'A']>=0 ) {
				s += b[j1];
				i = a_has[b[j1]-'A']+1;
				j = j1+1;
				added = true;
				break;
			}
			if ( i1<j1 ) {
				i1++;
			} else {
				j1++;
			}
		}
		if ( !added ) break;
	}

	cout << s << endl;

	return 0;
}