#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <string>
#include <iomanip>
#include <cmath>
#include <queue>
#include <map>
#include <stack>
#include <vector>
using namespace std;
#define long long LL
const int N = 1e3+5;
char a[N],b[N];
int lena,lenb,dp[N][N];
int main(){
	scanf("%s%s" , a + 1, b + 1);
	lena = strlen(a + 1);
	lenb = strlen(b + 1);
	for (int i = 1;i<=lena;i++)
	{
		for (int j = 1;j<=lenb;j++){
			if (a[i] == b[j]){
				dp[i][j] = dp[i - 1][j - 1] + 1; 
			}
			else{
				dp[i][j] = max(dp[i-1][j],dp[i][j-1]);
			}
		}
	}
	cout << dp[lena][lenb];
	return 0;
}

#include <bits/stdc++.h> using namespace std; int f[10001][10001]; void lcs(string c,string d,int o,int k){ if(o0||k0) return; if(c[o-1]==d[k-1]){ lcs(c,d,o-1,k-1); cout<<c[o-1]; } else if(f[o-1][k]>f[o][k-1])lcs(c,d,o-1,k); else lcs(c,d,o,k-1); } int main(){ string a,b; cin>>a>>b; int n=a.size(); int m=b.size(); for(int i=1;i<=n;i++){ for(int j=1;j<=m;j++){ if(a[i-1]==b[j-1])f[i][j]=f[i-1][j-1]+1; else f[i][j]=max(f[i-1][j],f[i][j-1]); } } cout<<f[n][m]; cout<<endl; lcs(a,b,n,m); return 0; }