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// ConsoleApplication3.cpp : Defines the entry point for the console application.
//

//#include "stdafx.h"
#include <iostream>
#include <math.h>
#include <iomanip>
#include <algorithm>
#include <fstream>
#include <string>
#include <map>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef string str;

const ll S = 10010;
const ll T = 1010;
const ll INF = 1e12;

str s, t;
ll dp[S][T], nx[S];
map <char, int> mp;

ifstream in;
ofstream out;

int main()
{
    //in.open("input.txt");
    //out.open("output.txt");
    cin >> s >> t;
    if (s[0] == t[0])
        dp[0][0] = 1;
    for (int i = 1; i < s.size(); i++)
        for (int j = 0; j < t.size(); j++)
                if (j)
                        dp[i][j] = min(dp[i - 1][j - 1], dp[i - 1][j] + (s[i] == t[j] ? 1 : 0));
                else
                    dp[i][j] = dp[i - 1][j] + (s[i] == t[j] ? 1 : 0);
    /*for (int i = 0; i < s.size(); i++, out << endl)
        for (int j = 0; j < t.size(); j++)
            out << dp[i][j] << ' ';
    /*ll mn = 0;
    for (int i = 0; i < t.size(); i++)
        if (dp[s.size() - 1][i] < dp[s.size() - 1][mn])
            mn = i;*/
    out << dp[s.size() - 1][t.size() - 1] << endl;
    str ans = "";
    ll i = s.size() - 1, j = t.size() - 1;
    while (i != 0)
    {
        if (dp[i][j] == dp[i - 1][j] + 1 && dp[s.size() - 1][t.size() - 1])
        {
            i--;
            dp[s.size() - 1][t.size() - 1]--;

            continue;
        }
        if (dp[i][j] == dp[i - 1][j - 1])
            j--;
        ans += s[i];
        i--;
    }
    if (!dp[s.size() - 1][t.size() - 1])
        ans += s[0];
    reverse(ans.begin(), ans.end());
    //out << s << endl;
    cout << ans << endl;
    //out << ans.size() << endl;
    //system("pause");
    return 0;
}

/*
abacaba
aba
*/