#include<iostream>
#include<fstream>
#include<vector>
#include<queue>
#include<string>
#include<math.h>
using namespace std;
#define BIT_TOOGLE(num, index) (num) |= (1<<(index))
#define BIT_CLEAR(num, index) (num) &= ~(1<<(index))

#define BIT_SET_VALUE(num, index, bit) \
if(bit)\
 	BIT_TOOGLE(num,index);\
else\
	BIT_CLEAR(num,index); 
bool bit_check(uint8_t num, uint8_t index){
	uint8_t mask=pow(2,index);
	mask&=num;
	if(mask==pow(2,index))
	return true;
	else
	return false;
}
int main(){
vector<unsigned short> line, line_cur;
vector<vector<uint8_t > >par;
string x,y;

getline(cin, x);
getline(cin, y);

uint8_t siz;
if((y.size())%4==0)
siz=(y.size())/4;
else
siz=(y.size())/4+1;
vector<uint8_t> temp2(siz,0);
vector<char> ans;

for(unsigned short i=0;i<=x.size();++i)
	par.push_back(temp2);
	
unsigned short m=x.size();
unsigned short n=y.size();
unsigned short cur;

for(unsigned short i=0;i<n+1;++i)
   	line.push_back(0);
	unsigned short prev=0;
   for(unsigned short i=1;i<m+1;++i){
   	line_cur.push_back(0);
     for(unsigned short j=1;j<n+1;++j){
       if(x[i-1]==y[j-1]){
         cur=line[j-1]+1;
         BIT_SET_VALUE(par[i][j],2*j%4,1);
         }
       else{
         if(line[j]>=prev){
           cur=line[j];
           par[i][j]=2;
           BIT_SET_VALUE(par[i][j],2*j%4+1,1);
           }
         else{
           cur=prev;
           BIT_SET_VALUE(par[i][j],2*j%4,1);
           BIT_SET_VALUE(par[i][j],2*j%4+1,1);
           }
           }
    prev=cur;
    line_cur.push_back(cur);
    }
    line=line_cur;
    prev=0;
    line_cur.clear();
    }
while(true){
	if(m==0||n==0)
	break;
	if(bit_check(par[m][n],2*n%4)&&!bit_check(par[m][n],2*n%4+1)){
		--m;
		--n;
		ans.push_back(x[m]);
	}
	else{
		if(!bit_check(par[m][n],2*n%4)&&bit_check(par[m][n],2*n%4+1))
			--m;
		else
			--n;
	}
}
for(int i=ans.size()-1;i>=0;i--){
cout<<ans[i];
}
cout<<endl;
}