#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
string a, b;
int dp[3005][3005];
pair backtrack[3005][3005];
char bukva[3005][3005];
int rec(int i, int j) {
    if(i == -1 or j == -1) {
        return 0;
    }
    if(dp[i][j] != -1) {
        return dp[i][j];
    }
    int result = 0;
    int r1 = -1, r2 = -1, r3 = -1;
    if(a[i] == b[j]) {
        r1 = rec(i - 1, j - 1) + 1;
    }
    r2 = rec(i - 1, j);
    r3 = rec(i, j - 1);
    result = max(r1, max(r2, r3));
    if(r1 == result) {
        backtrack[i][j] = make_pair(i - 1, j - 1);
        bukva[i][j] = a[i];
    }
    else if(r2 == result) {
        backtrack[i][j] = make_pair(i - 1, j);
        bukva[i][j] = '/';
    }
    else {
        backtrack[i][j] = make_pair(i, j - 1);
        bukva[i][j] = '/';
    }
    return dp[i][j] = result;
}
int main() {
    cin >> a >> b;
    memset(dp, -1, sizeof dp);
    
    rec(a.size() - 1, b.size() - 1);
    pair at = make_pair(a.size() - 1, b.size() - 1);
    string s = "";
    while(true) {
        if(at.first >= 0 and at.second >= 0) {
            s += bukva[at.first][at.second];
            at = make_pair(backtrack[at.first][at.second].first, backtrack[at.first][at.second].second);
        }
        else {
            break;
        }
    }
    for(int i = (int) s.size() - 1; i >= 0; i--) {
        if(s[i] != '/') {
            cout << s[i];
        }
    }
    return 0;
}
// 100 000 000