#include<bits/stdc++.h>
using namespace std;
#define nl "\n"
#define fi first
#define se second
#define pb push_back
#define ll long long
#define ull unsigned ll
#define RV  return void
#define sz(x) int(x.size())
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define fixed(n) fixed << setprecision(n)
#define cin(v) for (auto&i:v) cin >> i;
#define cout(v) for (auto&i:v) cout << i << " ";
#define clr(memo, x) memset(memo, x, sizeof memo)
#define FastCode ios_base::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);

void  Zainab(){
            // #ifndef ONLINE_JUDGE
              freopen("longpath.in", "r", stdin);
              freopen("longpath.out", "w", stdout);
            // #endif
}



int n , m;
string s,t;

vector < vector < int > > dp;

int rec(int i , int j ){
    if(i >=n or j >= m) return 0;

    int & ret = dp[i][j];
    if(~ret)
        return ret ;

    ret =0;
    if(s[i] == t[j])
        ret = max(ret , 1 + rec(i +1 , j+1));

    ret = max(ret , rec(i+1 , j));
    ret = max(ret , rec(i , j +1));



    return ret;
}



void build(int i , int j ){

    if(i >=n or j >= m) return ;

    int ret = dp[i][j];

    if(s[i] == t[j] and ret == dp[i+1][j+1] +1 ) {
        cout << s[i] ;
        build(i+1 , j+1);
        return ;
    }

    if(ret == dp[i][j+1]){
        build(i , j+1);

    }
    else if(ret == dp[i+1][j]){

        build(i+1 , j);
    }

}
void myCode(){

cin >> s >> t;
n=sz(s) , m = sz(t);

dp.assign(n+1 , vector < int > (m+1 , -1));

int len= rec(0,0);
cout << len << nl;

build(0,0);


}


int main(){
                                   FastCode ;
                                    //  Zainab() ;

    int testCase=1;
        //   cin >> testCase ;

      for(int i=1 ; i<= testCase ; i++)
        myCode();

    return 0;
}