#include <iostream>
#include <sstream>
#include <iomanip>
#include <vector>
#include <string>
#include <map>
#include <set>
#include <algorithm>
#include <numeric>
#include <iterator>
#include <functional>
#include <complex>
#include <queue>
#include <stack>
#include <cmath>
#include <cassert>
using namespace std;
typedef long long LL;
typedef long double LD;
typedef complex<LD> CMP;

template<typename T>
struct DP2
{
	const int N1, N2;
	vector<T> data;
	DP2(int N1, int N2, const T& t = T())
		: N1(N1), N2(N2), data(N1*N2, t) { assert(data.size()*sizeof(T)<(1<<26)); }
	T& operator()(int i1, int i2)
		{ return data[ (i1*N2)+i2 ]; }
	void swap(DP2& rhs)
		{ data.swap(rhs.data); }
};

class TheLargestString { public:
	string find(string s, string t)
	{
		const int N = s.size();
		DP2< pair<string,string> > best(N+1,N+1);
		for(int i=N-1; i>=0; --i)
		{
			for(int len=1; len<=N-i; ++len)
			{
				pair<string, string> cand = best(i+1, len);
				pair<string, string> cand2(s[i]+best(i+1, len-1).first, t[i]+best(i+1,len-1).second);
				if(cand.first+cand.second < cand2.first+cand2.second)
					cand = cand2;
				best(i, len) = cand;
			}
		}
		string ans;
		for(int len=0; len<=N; ++len)
			ans = max(ans, best(0,len).first + best(0,len).second);
		return ans;
	}
};

// BEGIN CUT HERE
#include <ctime>
double start_time; string timer()
 { ostringstream os; os << " (" << int((clock()-start_time)/CLOCKS_PER_SEC*1000) << " msec)"; return os.str(); }
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v)
 { os << "{ ";
   for(typename vector<T>::const_iterator it=v.begin(); it!=v.end(); ++it)
   os << '\"' << *it << '\"' << (it+1==v.end() ? "" : ", "); os << " }"; return os; }
void verify_case(const string& Expected, const string& Received) {
 bool ok = (Expected == Received);
 if(ok) cerr << "PASSED" << timer() << endl;  else { cerr << "FAILED" << timer() << endl;
 cerr << "\to: \"" << Expected << '\"' << endl << "\tx: \"" << Received << '\"' << endl; } }
#define CASE(N) {cerr << "Test Case #" << N << "..." << flush; start_time=clock();
#define END	 verify_case(_, TheLargestString().find(s, t));}
int main(){
CASE(0)
	string s = "ab"; 
	string t = "zy"; 
	string _ = "by"; 
END
CASE(1)
	string s = "abacaba"; 
	string t = "zzzaaaa"; 
	string _ = "cbaaaa"; 
END
CASE(2)
	string s = "x"; 
	string t = "x"; 
	string _ = "xx"; 
END
CASE(3)
	string s = "abbabbabbababaaaabbababab"; 
	string t = "bababbaabbbababbbbababaab"; 
	string _ = "bbbbbbbbbbbbbbbbbbaaab"; 
END
/*
CASE(4)
	string s = ; 
	string t = ; 
	string _ = ; 
END
CASE(5)
	string s = ; 
	string t = ; 
	string _ = ; 
END
*/
}
// END CUT HERE
