#include<bits/stdc++.h> 
using namespace std;
#define LL long long
const int N=1e3+11;
struct node
{
	int data,i,j;
}dp[N][N];
int lena,lenb;
string a,b,ans;
int main()
{
	cin>>a>>b;
	lena=a.size();
	lenb=b.size();
	for(int i=1;i<=lena;i++)
	{
		for(int j=1;j<=lenb;j++)
		{
			if(a[i-1]==b[j-1])
			{
				dp[i][j].data=dp[i-1][j-1].data+1;
				dp[i][j].i=i;
				dp[i][j].j=j;
			}
			else if(dp[i-1][j].data>dp[i][j-1].data)
			{
				dp[i][j].data=dp[i-1][j].data;
				dp[i][j].i=dp[i-1][j].i;
				dp[i][j].j=dp[i-1][j].j;
			}
			else
			{
				dp[i][j].data=dp[i][j-1].data;
				dp[i][j].i=dp[i][j-1].i;
				dp[i][j].j=dp[i][j-1].j;
			} 
		}
	}
	cout<<dp[lena][lenb].data<<endl;
	for(int i=dp[lena][lenb].i,j=dp[lena][lenb].j;i|j;)
	{
		ans=a[i-1]+ans;
		int tmp=dp[i-1][j-1].i;
		j=dp[i-1][j-1].j;
		i=tmp;
	}cout<<ans;
   	return 0;
}