#include <bits/stdc++.h>
using namespace std;

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define FOR(i, a, b) for (int i = (a); i<(b); ++i)
#define RFOR(i, b, a) for (int i = (b)-1; i>=(a); --i)
#define MP make_pair
#define PB push_back
#define F first
#define S second
#define FILL(a, b) memset(a, b, sizeof(a))

typedef long long LL;
typedef pair<int, int> PII;
typedef vector<int> VI;

const int N = 1'000'047;
const int MAGIC = 50;

int dp[MAGIC + 2][MAGIC + 2];

void upd(int& a, int b){
	a = max(a, b);
}

string solve(string a, string b){
	int n = SZ(a);
	FOR(i, 0, n + 1)
	FOR(j, 0, n + 1)
		dp[i][j] = 0;
	
	FOR(i, 0, n + 1){
		FOR(j, 0, n + 1){
			if(i + 1 <= n)
				upd(dp[i + 1][j], dp[i][j]);
			if(j + 1 <= n)
				upd(dp[i][j + 1], dp[i][j]);
			if(i + 1 <= n && j + 1 <= n && a[i] == b[j])
				upd(dp[i + 1][j + 1], dp[i][j] + 1);
		}
	}
	string res = "";
	int i = n, j = n;
	while(i > 0 || j > 0){
		if(i > 0 && dp[i - 1][j] == dp[i][j]){
			i--;
			continue;
		}
		if(j > 0 && dp[i][j - 1] == dp[i][j]){
			j--;
			continue;
		}
		assert(i > 0 && j > 0 && dp[i - 1][j - 1] + 1 == dp[i][j] && a[i - 1] == b[j - 1]);
		res += a[i - 1];
		i--;
		j--;
 	}
 	reverse(ALL(res));
	return res;
} 


int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	
	
	int n;
	cin >> n;
	
	string a, b;
	cin >> a >> b;

	string res = "";
	FOR(i, 0, n/MAGIC + 1)
		res += solve(a.substr(MAGIC * i, MAGIC), b.substr(MAGIC * i, MAGIC));
	
	
	//assert(SZ(res) >= n / 2);
	cout << res << endl;
	
	
	return 0;
}