#include <bits/stdc++.h>
using namespace std;
string t[101][101];
string SCS(string a, string b,int n , int m){
for(int i=0 ; i<n+1 ; i++){
for(int j=0 ; j<m+1 ; j++){
if(i==0||j==0){
t[i][j]=" ";
}
if(a[i-1]==b[j-1]){
t[i][j] = t[i-1][j-1]+(a[i-1]);
}else{
if(a[i-1]<b[j-1]){
t[i][j] = t[i-1][j]+a[i-1];
}else{
t[i][j] = t[i][j]+b[j-1];
}
}
}
}
return t[n][m];
}
int main() {
string a;
string b;
cin>>a;
cin>>b;
int n = a.length();
int m = b.length();
cout<<SCS(a,b,n,m);
return 0;
}
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