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

bccdb
 z
 dfdeed
 aab
 y
 abac

//package round414;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;

public class C {
	InputStream is;
	PrintWriter out;
	String INPUT = "";
	
	void solve()
	{
		char[] s = ns().toCharArray();
		char[] t = ns().toCharArray();
		int[] fs = new int[26];
		for(char c : s)fs[c-'a']++;
		int[] ft = new int[26];
		for(char c : t)ft[c-'a']++;
		int n = s.length;
		
		char[] ans = new char[n];
		for(int i = 0;i < n;i++){
			if(min(fs) >= max(ft)){
				if(i % 2 == 0){
					if(n % 2 == 0){
						for(int j = i+1;j < n;j+=2){
							int minfs = min(fs);
							ans[j] = (char)('a'+minfs);
							fs[minfs]--;
						}
						for(int j = i;j < n;j+=2){
							int maxft = max(ft);
							ans[j] = (char)('a'+maxft);
							ft[maxft]--;
						}
					}else{
						for(int j = i;j < n;j+=2){
							int minfs = min(fs);
							ans[j] = (char)('a'+minfs);
							fs[minfs]--;
						}
						for(int j = i+1;j < n;j+=2){
							int maxft = max(ft);
							ans[j] = (char)('a'+maxft);
							ft[maxft]--;
						}
					}
					break;
				}else{
					if(n % 2 == 1){
						for(int j = i;j < n;j+=2){
							int minfs = min(fs);
							ans[j] = (char)('a'+minfs);
							fs[minfs]--;
						}
						for(int j = i+1;j < n;j+=2){
							int maxft = max(ft);
							ans[j] = (char)('a'+maxft);
							ft[maxft]--;
						}
					}else{
						for(int j = i+1;j < n;j+=2){
							int minfs = min(fs);
							ans[j] = (char)('a'+minfs);
							fs[minfs]--;
						}
						for(int j = i;j < n;j+=2){
							int maxft = max(ft);
							ans[j] = (char)('a'+maxft);
							ft[maxft]--;
						}
					}
				}
				break;
			}
			if(i % 2 == 0){
				int minfs = min(fs);
				ans[i] = (char)('a'+minfs);
				fs[minfs]--;
			}else{
				int maxft = max(ft);
				ans[i] = (char)('a'+maxft);
				ft[maxft]--;
			}
		}
		out.println(new String(ans));
	}
	
	int max(int[] f)
	{
		for(int i = f.length-1;i >= 0;i--){
			if(f[i] > 0)return i;
		}
		return -1;
	}
	
	int min(int[] f)
	{
		for(int i = 0;i < f.length;i++){
			if(f[i] > 0)return i;
		}
		return -1;
	}
	
	void run() throws Exception
	{
		is = oj ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);
		
		long s = System.currentTimeMillis();
		solve();
		out.flush();
		tr(System.currentTimeMillis()-s+"ms");
	}
	
	public static void main(String[] args) throws Exception { new C().run(); }
	
	private byte[] inbuf = new byte[1024];
	public int lenbuf = 0, ptrbuf = 0;
	
	private int readByte()
	{
		if(lenbuf == -1)throw new InputMismatchException();
		if(ptrbuf >= lenbuf){
			ptrbuf = 0;
			try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
			if(lenbuf <= 0)return -1;
		}
		return inbuf[ptrbuf++];
	}
	
	private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
	private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
	
	private double nd() { return Double.parseDouble(ns()); }
	private char nc() { return (char)skip(); }
	
	private String ns()
	{
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	
	private char[] ns(int n)
	{
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while(p < n && !(isSpaceChar(b))){
			buf[p++] = (char)b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}
	
	private char[][] nm(int n, int m)
	{
		char[][] map = new char[n][];
		for(int i = 0;i < n;i++)map[i] = ns(m);
		return map;
	}
	
	private int[] na(int n)
	{
		int[] a = new int[n];
		for(int i = 0;i < n;i++)a[i] = ni();
		return a;
	}
	
	private int ni()
	{
		int num = 0, b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private long nl()
	{
		long num = 0;
		int b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private boolean oj = System.getProperty("ONLINE_JUDGE") != null;
	private void tr(Object... o) { if(!oj)System.out.println(Arrays.deepToString(o)); }
}
