> #include <iostream>
> #include <iomanip>
> #include <cmath>
> #include <string>
> using namespace std;
> 
> #define min(a, b)  ((a) < (b) ? (a):(b))
> 
> string a, b;
> string insa;
> string insb;
> 
> bool isPalindrome(string& s, string& ins, bool tail)
> {    
> 	 int i, j;
> 	 if(tail)
> 	 {
> 		 for(i = ins.length(), j = s.length() - 1; i < j; i ++, j --)
> 		 {
> 			 if(s[i] != s[j])
> 				 break;
> 		 }
> 		 if(i >= j)
> 		 {
> 			 return true;
> 		 }
> 	 }
> 	 else
> 	 {
> 		 string temps = s + ins;
> 		 for(i = 0, j = temps.length() - 1; i < j; i ++, j --)
> 		 {
> 			  if(temps[i] != temps[j])
> 				 break;
> 		 }
> 		 if(i >= j)
> 		 {
> 			 return true;
> 		 }
> 	 }
> 
> 	 return false;
> }
> 
> bool ok()
> {
> 	bool aaok = isPalindrome(a, insa, true);
> 	bool baok = isPalindrome(b, insa, false);
> 	bool abok = isPalindrome(a, insb, false);
> 	bool bbok = isPalindrome(b, insb, true);
> 	bool a = (aaok && !baok) || (!aaok && baok);
> 	bool b = (abok && !bbok) || (!abok && bbok);
> 	if(a && !b)
> 	{	
> 		cout << insa << endl;
> 		return true;
> 	}
> 	else if(!a && b)
> 	{	
>         cout << insb << endl;
> 		return true;
> 	}
> 	else if(a && b)
> 	{
> 		cout << min(insa, insb) << endl;
> 		return true;
> 	}
> 	else
> 	{
> 		return false;
> 	}	
> }
> void main()
> {
> 
> 	while(cin >> a >> b)
> 	{
> 		int i;    
> 
>         if(a == b)
> 			cout << "No Solution." << endl;
> 		else
> 		{
> 			 int lena = a.length();
> 			 int lenb = b.length();
> 			 if(lena > lenb)
> 			 {
> 				 int ltemp = lena;
> 				 lena = lenb;
> 				 lenb = ltemp;
> 				 string stemp = a;
> 				 a = b;
> 				 b = stemp;							 
> 			 }
>              insa = "";
> 			 insb = "";
> 			 for(i = 0; i <= lena; i ++)
> 			 {
> 				 if(ok())
> 				 {
> 					break;
> 				 }        
>                  if(i < lena)
> 				 {
> 				     insa.insert(0, a[i]);
> 				     insb.insert(0, b[i]);
> 				 }				 
> 			 }
> 			 if(i == lena + 1) 
> 			 {
> 				 if(b[lena] == 'a')
> 				 {
> 					 insa.insert(0, 'b');
> 					 cout << insa << endl;
> 				 }
> 				 else
> 				 {  
> 					 insa.insert(0, 'a');
> 					 cout << insa << endl;
> 				 }
> 			 }			 
> 		}
> 	}
> 
> } 
> 
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