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

string a, b, s;
int n, m;
int f[3005][3005];

int main() {
    cin >> a >> b;
    n = a.size(), m = b.size();
    a = " " + a;
    b = " " + b;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= m; j++) {
            if (a[i] == b[j]) f[i][j] = f[i - 1][j - 1] + 1;
            else f[i][j] = max(f[i - 1][j], f[i][j - 1]);
        }
    }
    for (int i = 1; i <= f[n][m] + 114; i++) s += "";
	int l = n, r = m;
	while (f[l][r]) {
		if (a[l] == b[r]) {
	        s[f[l][r]] = a[l];
	        l--, r--;
	    }
		else {
			if (f[l][r] == f[l - 1][r]) l--;
			else r--;
		}
	}
	for (int i = 1; i <= f[n][m]; i++) cout << s[i];
    return 0;
}

非常经典的写法，不知道为什么 RE