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#include<bits/stdc++.h>
using namespace std;

string s1, s2;
deque<char>q1, q2, q3;
bool flag = true;
bool flag1 = true;

void Input_deque() {
int len1 = s1.length(), len2 = s2.length();
for(int i = 0; i < len1; i++) q1.push_back(s1[i]);
for(int i = 0; i < len2; i++) q2.push_back(s2[i]);
}

void Output_deque(deque<char>q) {
int siz = q.size();
while(!q.empty()) {
cout << q.front();
q.pop_front();
}
}

int main() {
ios::sync_with_stdio(false);
cin>>s1>>s2;
Input_deque();

while(1) {
if(flag == true) {

	char a = q1.front();   	q1.pop_front();  
	q3.push_back(a);				
	if(count(q3.begin(), q3.end(), a) >= 2) {	
		q3.pop_back();    q1.push_back(a);	
		while(1) {
			char c = q3.back();
			q3.pop_back();
			q1.push_back(c);
			if(c == a) break;
		}
		flag = true; continue;		
	} 
}
flag = false;

if(q1.empty()) { flag1=false; break;}
else if(q2.empty()) break;	
 
 
if(flag == false) {
	char b = q2.front();    q2.pop_front();
	q3.push_back(b);
	if(count(q3.begin(), q3.end(), b) >= 2) {
		q3.pop_back();    q2.push_back(b);	
		while(1) {
			char c = q3.back();
			q3.pop_back();
			q2.push_back(c);
			if(c == b) break;
		}
		flag = false; continue;			
	}
}
flag = true;
if(q1.empty()) { flag1=false; break;}
else if(q2.empty()) break;	

}

if(flag1 == false)
Output_deque(q2);
else Output_deque(q1);
return 0;
}