#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main(){
	string a, b;
	cin >> a >> b;
	int a_size = a.size(), b_size = b.size();
	vector<vector<pair<int, string>>> dp(a.size() + 1, vector<pair<int, string>>(b_size + 1, {0, ""}));
	for(int i = 1; i <= a_size; i++){
		for(int j = 1; j <= b_size; j++){
			if(a[i - 1] == b[j - 1]) {
				dp[i][j].first = dp[i - 1][j - 1].first + 1;
				string tmp = dp[i - 1][j - 1].second;
				tmp.push_back(a[i - 1]);
				dp[i][j].second = tmp;
			}
			else{
				dp[i][j].first = max(dp[i - 1][j].first, dp[i][j - 1].first);
				if(dp[i - 1][j].first > dp[i][j - 1].first){
					dp[i][j].second = dp[i - 1][j].second;
				}
				else dp[i][j].second = dp[i][j - 1].second;
				
			}
		}
	}
	//cout << dp[a_size][b_size].first << " " << dp[a_size][b_size].second << endl;
	cout << dp[a_size][b_size].second << endl;
	return 0;
}