bcdef
abbbc
 z
y
 reddit
abcdef
 abc
aaa
 y
z
 cbxz
aaaa

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.util.Scanner;
import java.io.*;
import java.util.*;
import java.math.*;
import java.lang.*;
 
import static java.lang.Math.*;
 
public class Main implements Runnable
{
	static class InputReader
	{
		private InputStream stream;
		private byte[] buf = new byte[1024];
		private int curChar;
		private int numChars;
		private SpaceCharFilter filter;
		
		public InputReader(InputStream stream)
		{
			this.stream = stream;
		}
		
		public int read()
		{
			if (numChars==-1) 
				throw new InputMismatchException();
			
			if (curChar >= numChars)
			{
				curChar = 0;
				try 
				{
					numChars = stream.read(buf);
				}
				catch (IOException e)
				{
					throw new InputMismatchException();
				}
				
				if(numChars <= 0)				
					return -1;
			}
			return buf[curChar++];
		}
	 
		public String nextLine()
		{
			BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
			String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
		}
		public int nextInt()
		{
			int c = read();
			
			while(isSpaceChar(c)) 
				c = read();
			
			int sgn = 1;
			
			if (c == '-') 
			{
				sgn = -1;
				c = read();
			}
			
			int res = 0;
			do 
			{
				if(c<'0'||c>'9') 
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();
			}
			while (!isSpaceChar(c)); 
			
			return res * sgn;
		}
		
		public long nextLong() 
		{
			int c = read();
			while (isSpaceChar(c))
				c = read();
			int sgn = 1;
			if (c == '-') 
			{
				sgn = -1;
				c = read();
			}
			long res = 0;
			
			do 
			{
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();
			}
			while (!isSpaceChar(c));
				return res * sgn;
		}
		
		public double nextDouble() 
		{
			int c = read();
			while (isSpaceChar(c))
				c = read();
			int sgn = 1;
			if (c == '-') 
			{
				sgn = -1;
				c = read();
			}
			double res = 0;
			while (!isSpaceChar(c) && c != '.') 
			{
				if (c == 'e' || c == 'E')
					return res * Math.pow(10, nextInt());
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();
			}
			if (c == '.') 
			{
				c = read();
				double m = 1;
				while (!isSpaceChar(c)) 
				{
					if (c == 'e' || c == 'E')
						return res * Math.pow(10, nextInt());
					if (c < '0' || c > '9')
						throw new InputMismatchException();
					m /= 10;
					res += (c - '0') * m;
					c = read();
				}
			}
			return res * sgn;
		}
		
		public String readString() 
		{
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do 
			{
				res.appendCodePoint(c);
				c = read();
			} 
			while (!isSpaceChar(c));
			
			return res.toString();
		}
	 
		public boolean isSpaceChar(int c) 
		{
			if (filter != null)
				return filter.isSpaceChar(c);
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}
	 
		public String next() 
		{
			return readString();
		}
		
		public interface SpaceCharFilter 
		{
			public boolean isSpaceChar(int ch);
		}
	}
 
	static class Pair implements Comparable<Pair>
	{
		long a;
		int index;

		public Pair(long a,int index)
		{
			this.a=a;
			this.index=index;
		}
 		
		public int compareTo(Pair pair)
		{
			//if(Long.compare(a,pair.a)==0)
			//	return Integer.compare(b,pair.b);
			return Long.compare(a,pair.a);
		}
	}
 	
	public static void main(String args[]) throws Exception
	{
		new Thread(null, new Main(),"CHECK2",1<<32).start();
	}	

 	
	public void run()
	{
		InputReader sc=new InputReader(System.in);
		PrintWriter w=new PrintWriter(System.out);
 
 		char c[]=sc.next().toCharArray();
 		char c1[]=sc.next().toCharArray();

 		Arrays.sort(c);
 		Arrays.sort(c1);
 		
 		int n=c.length;

 		int f1=0;
 		int b1=n-1;

 		int f2=0;
 		int b2=n-1;
 		char ans[]=new char[n];

 		int f3=0;
 		int b3=n-1;
		for(int i=0;i<n;i++)
		{
			if(i%2==0)
			{
				if(c[f1]<c1[b1])
				{
					ans[f3++]=c[f1++];
				}
				else if(c[f1]>c1[b1])
				{
					ans[b3--]=c[f1++];
				}
				else
				{
ans[f3++]=c[f1++];
				}
			}
			else
			{
				if(c[f1]<c1[b1])
				{
					ans[f3++]=c1[b1--];
				}
				else if(c[f1]>c1[b1])
				{
					ans[b3--]=c1[b1--];
				}
				else
				{
					ans[f3++]=c1[b1--];
				}
			}
		} 		
		w.println(new String(ans));

 		w.close();
	}
}
