#define _CRT_SECURE_NO_WARNINGS
#define _CRT_DISABLE_PERFCRIT_LOCKS
#include <iostream>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<bitset>

using namespace std;

typedef long long ll;

const ll IN = ll(1e9);

vector<int> w;
int n, a;
ll test(bitset<20> a) {
	ll s = 0;
	for (int j = 0; j < n; j++) {
		if (a[j])
			s += w[j];
		else
			s -= w[j];

	}
	return abs(s);
}
ll binpow(int a, int n) {
	if (n == 0)
		return 1;
	if (n % 2 == 1)
		return binpow(a, n - 1) * a;
	else {
		ll b = binpow(a, n / 2);
		return b * b;
	}
}
string ans = "";
string a1 = "";
string a2 = "";
vector<vector<int>> temp(1001, vector<int>(1001, 2));
int Solve(int a, int b, int x, int y) {
	if (x >= n && y >= n) {
		return 1;
	}
	if (temp[x][y] == 2) {
		if (abs(a - b) > 1) {
			temp[x][y] = 0;
			return 0;
		}
		else {
			int t1 = 0;
			if (x < n) {
				if (a1[x] == '1')
					t1 = Solve(a, b + 1, x + 1, y);
				else
					t1 = Solve(a + 1, b, x + 1, y);
			}
			if (t1) {
				ans += "1";
				return 1;
			}
			int t2 = 0;
			if (y < n) {
				if (a2[y] == '1')
					t2 = Solve(a, b + 1, x, y + 1);
				else
					t2 = Solve(a + 1, b, x, y + 1);
			}
			if (t2) {
				ans += "2";
				return 1;
			}
			temp[x][y] = 0;
			return 0;
		}
	}
	else
		return temp[x][y];

}


int main()
{

	cin >> n;
	cin >> a1;
	cin >> a2;
	bool s = Solve(0, 0, 0, 0);
	if (s) {
		reverse(ans.begin(), ans.end());
		cout << ans;
	}
	else
		cout << "Impossible";
	//system("pause");
	return 0;
}