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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.io.*;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.*;

public class Main {
	static class Reader 
    { 
        final private int BUFFER_SIZE = 1 << 16; 
        private DataInputStream din; 
        private byte[] buffer; 
        private int bufferPointer, bytesRead; 
  
        public Reader() 
        { 
            din = new DataInputStream(System.in); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public Reader(String file_name) throws IOException 
        { 
            din = new DataInputStream(new FileInputStream(file_name)); 
            buffer = new byte[BUFFER_SIZE]; 
            bufferPointer = bytesRead = 0; 
        } 
  
        public String readLine() throws IOException 
        { 
            byte[] buf = new byte[(int) (2e6+10)]; // line length 
            int cnt = 0, c; 
            while ((c = read()) != -1) 
            { 
                if (c == '\n') 
                    break; 
                buf[cnt++] = (byte) c; 
            } 
            return new String(buf, 0, cnt); 
        } 
  
        public int nextInt() throws IOException 
        { 
            int ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do
            { 
                ret = ret * 10 + c - '0'; 
            }  while ((c = read()) >= '0' && c <= '9'); 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public long nextLong() throws IOException 
        { 
            long ret = 0; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        public double nextDouble() throws IOException 
        { 
            double ret = 0, div = 1; 
            byte c = read(); 
            while (c <= ' ') 
                c = read(); 
            boolean neg = (c == '-'); 
            if (neg) 
                c = read(); 
  
            do { 
                ret = ret * 10 + c - '0'; 
            } 
            while ((c = read()) >= '0' && c <= '9'); 
  
            if (c == '.') 
            { 
                while ((c = read()) >= '0' && c <= '9') 
                { 
                    ret += (c - '0') / (div *= 10); 
                } 
            } 
  
            if (neg) 
                return -ret; 
            return ret; 
        } 
  
        private void fillBuffer() throws IOException 
        { 
            bytesRead = din.read(buffer, bufferPointer = 0, BUFFER_SIZE); 
            if (bytesRead == -1) 
                buffer[0] = -1; 
        } 
  
        private byte read() throws IOException 
        { 
            if (bufferPointer == bytesRead) 
                fillBuffer(); 
            return buffer[bufferPointer++]; 
        } 
  
        public void close() throws IOException 
        { 
            if (din == null) 
                return; 
            din.close(); 
        } 
    }

	public static PrintWriter out = new PrintWriter (new BufferedOutputStream(System.out));
	public static Reader sc = new Reader();

	public static long[][] dp;
	public static int[][] tab;
	
	public static void main(String[] args) throws IOException{

		char[] a = sc.readLine().trim().toCharArray();
		char[] b = sc.readLine().trim().toCharArray();
		Arrays.sort(a);
		Arrays.sort(b);
		
		MultiSet<Character> seta = new MultiSet<>();
		MultiSet<Character> setb = new MultiSet<>();
		for(int i=0;i<(a.length+1)/2;++i) seta.add(a[i]);
		for(int i=0;i<b.length/2;++i) setb.add(b[a.length-1-i]);
		
		char[] ans = new char[a.length];
		Arrays.fill(ans,'x');
		int j = a.length-1,i = 0;
		int p = 0;
		while(i <= j) {
			if(p == 0) {
				char min = seta.first();
				if(setb.size() > 0 && min >= setb.last()) {
					ans[j--] = seta.last();
					seta.delete(seta.last());
				}else {
					ans[i++] = min;
					seta.delete(min);
				}
				
				p^=1;
			}else {
				char max = setb.last();
				if(seta.size() > 0 && max <= seta.first()) {
					ans[j--] = setb.first();
					setb.delete(setb.first());
				}else {
					ans[i++] = max;
					setb.delete(max);
				}
				p^=1;
				
			}
		
		}
		out.print(new String(ans));
		out.close();
	}
	
static class MultiSet<T>{
		private TreeMap<T,Integer> map = new TreeMap<>();
		
		public void add(T key) {
			map.put(key,map.getOrDefault(key,0)+1);
		}
		
		public void delete(T key) {
			if(map.containsKey(key)) {
				int val = map.get(key);
				if(val == 1) map.remove(key);
				else map.replace(key,val-1);
			}
		}
		
		public void deleteAll(T key) {
			map.remove(key);
		}
		
		public int count(T key) {
			return map.get(key);
		}
		
		public void show() {
			System.out.println(map);
		}
		
		public int size() {
			return map.size();
		}
		
		public T first(){
            return map.firstKey();
        }
		
		 public T last(){
	            return map.lastKey();
	        }
	        
	        public T ceiling(T x){
	            return map.ceilingKey(x);
	        }
	        public T floor(T x){
	            return map.floorKey(x);
	        }
	        
	        public T higher(T x){
	            return map.higherKey(x);
	        }
	        
	        public T lower(T x){
	            return map.lowerKey(x);
	        }

		
	}


}