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

bccdb
 z
 dfdeed
 aab
 y
 abac


import java.util.*;
import java.io.*;

/**
 *
 * @author usquare
 * 
 */

public class ProblemA {

    public static int mod = (int) (1e9+7);
    public static InputReader in;
    public static PrintWriter out;
    
    public static void main(String[] args) throws FileNotFoundException {

        in = new InputReader(System.in);
        out = new PrintWriter(System.out);
        
        char[] a=in.readString().toCharArray();
        char[] b=in.readString().toCharArray();
        Arrays.sort(a);
        Arrays.sort(b);
        int n=a.length;
        
        int[] aa=new int[26];
        int[] bb=new int[26];
        
        for(int i=0;i<(n+1)/2;i++){
            aa[(int)(a[i]-'a')]++;
        }

        for(int i=(n+1)/2;i<n;i++){
            bb[(int)(b[i]-'a')]++;
        }
        
        char[] ans=new char[n];
        int l=0;
        int r=n-1;
        for(int i=0;i<n;i++){
            if((i&1)==0){
                boolean f=false;
                int cur=0;
                for(int j=0;j<26;j++) 
                    if(aa[j]>0){
                        cur=j;
                        break;
                    }
                for(int j=cur+1;j<26;j++)
                    if(bb[j]>0){
                        f=true;
                        break;
                    }
                //debug(i,f,cur);
                if(!f){
                    for(int j=25;j>=0;j--)
                        if(aa[j]>0){
                            aa[j]--;
                            ans[r--]=(char)(j+'a');
                            break;
                        }
                }
                else{
                    aa[cur]--;
                    ans[l++]=(char)(cur+'a');
                }
            }
            else{
                boolean f=false;
                int cur=0;
                for(int j=25;j>=0;j--) 
                    if(bb[j]>0){
                        cur=j;
                        break;
                    }
                for(int j=cur-1;j>=0;j--)
                    if(aa[j]>0){
                        f=true;
                        break;
                    }
                if(!f){
                    for(int j=0;j<26;j++)
                        if(bb[j]>0){
                            bb[j]--;
                            ans[r--]=(char)(j+'a');
                            break;
                        }
                }
                else{
                    bb[cur]--;
                    ans[l++]=(char)(cur+'a');
                }
                
            }
        }
        
        out.println(new String(ans));

        out.close();
    }
    
    static class Pair implements Comparable<Pair>{

        long x,y;
        
//	Pair (int x,int y,int i){
//		this.x=x;
//		this.y=y;
//		this.i=i;
//	}

	Pair (long x,long y){
		this.x=x;
		this.y=y;
	}
        
	public int compareTo(Pair o) {
                    return Long.compare(this.x,o.x);
		//return 0;
	}

        public boolean equals(Object o) {
            if (o instanceof Pair) {
                Pair p = (Pair)o;
                return p.x == x && p.y == y ;
            }
            return false;
        }
        public int hashCode() {
            return new Long(x).hashCode() * 31 + new Long(y).hashCode();
        }
    
    } 
    
    static long[] shuffle(long[] a, Random gen){ 
        for(int i = 0, n = a.length;i < n;i++){ 
            int ind = gen.nextInt(n-i)+i; 
            long d = a[i]; 
            a[i] = a[ind]; 
            a[ind] = d; 
        } 
        return a; 
    }

        
    public static long add(long a,long b){
        long x=(a+b);
        while(x>=mod) x-=mod;
        return x;
    }

    public static long sub(long a,long b){
        long x=(a-b);
        while(x<0) x+=mod;
        return x;
    }
    
    public static long mul(long a,long b){
        a%=mod;
        b%=mod;
        long x=(a*b);
        return x%mod;
    }
    
    static boolean isPal(String s){
        for(int i=0, j=s.length()-1;i<=j;i++,j--){
                if(s.charAt(i)!=s.charAt(j)) return false;
        }
        return true;
    }
    static String rev(String s){
            StringBuilder sb=new StringBuilder(s);
            sb.reverse();
            return sb.toString();
    }

    static long gcd(long x,long y){
        if(y==0) return x;
    if(x%y==0)
            return y;
    else
            return gcd(y,x%y);
    }

    static int gcd(int x,int y){
        if(y==0) return x;
    if(x%y==0)
            return y;
    else 
            return gcd(y,x%y);
    }

    static long gcdExtended(long a,long b,long[] x){

        if(a==0){
            x[0]=0;
            x[1]=1;
            return b;
        }
        long[] y=new long[2];
        long gcd=gcdExtended(b%a, a, y);

        x[0]=y[1]-(b/a)*y[0];
        x[1]=y[0];

        return gcd;
    }

    static int abs(int a,int b){
    return (int)Math.abs(a-b);
    }

    static long abs(long a,long b){
    return (long)Math.abs(a-b);
    }

    static int max(int a,int b){
    if(a>b)
            return a;
    else
            return b;
    }

    static int min(int a,int b){
    if(a>b)
            return b;
    else 
            return a;
    }

    static long max(long a,long b){
    if(a>b)
            return a;
    else
            return b;
    }

    static long min(long a,long b){
    if(a>b)
            return b;
    else 
            return a;
    }


    public static long pow(long n,long p,long m){
	 long  result = 1;
	  if(p==0)
	    return 1;
          
	while(p!=0)
	{
	    if(p%2==1)
	        result *= n;
	    if(result>=m)
	    result%=m;
	    p >>=1;
	    n*=n;
	    if(n>=m)
	    n%=m;
	}
	return result;
    }
    
    public static long pow(long n,long p){
	long  result = 1;
	  if(p==0)
	    return 1;
          
	while(p!=0)
	{
	    if(p%2==1)
	        result *= n;	    
	    p >>=1;
	    n*=n;	    
	}
	return result;
    }
    
     static void debug(Object... o) {
            System.out.println(Arrays.deepToString(o));
    }

    static class InputReader {

            private final InputStream stream;
            private final byte[] buf = new byte[8192];
            private int curChar, snumChars;
            private SpaceCharFilter filter;

            InputReader(InputStream stream) {
                    this.stream = stream;
            }

            int snext() {
                    if (snumChars == -1)
                            throw new InputMismatchException();
                    if (curChar >= snumChars) {
                            curChar = 0;
                            try {
                                    snumChars = stream.read(buf);
                            } catch (IOException e) {
                                    throw new InputMismatchException();
                            }
                            if (snumChars <= 0)
                                    return -1;
                    }
                    return buf[curChar++];
            }

            int nextInt() {
                    int c = snext();
                    while (isSpaceChar(c)) {
                            c = snext();
                    }
                    int sgn = 1;
                    if (c == '-') {
                            sgn = -1;
                            c = snext();
                    }
                    int res = 0;
                    do {
                            if (c < '0' || c > '9')
                                    throw new InputMismatchException();
                            res *= 10;
                            res += c - '0';
                            c = snext();
                    } while (!isSpaceChar(c));
                    return res * sgn;
            }

            long nextLong() {
                    int c = snext();
                    while (isSpaceChar(c)) {
                            c = snext();
                    }
                    int sgn = 1;
                    if (c == '-') {
                            sgn = -1;
                            c = snext();
                    }
                    long res = 0;
                    do {
                            if (c < '0' || c > '9')
                                    throw new InputMismatchException();
                            res *= 10;
                            res += c - '0';
                            c = snext();
                    } while (!isSpaceChar(c));
                    return res * sgn;
            }

            int[] nextIntArray(int n) {
                    int a[] = new int[n];
                    for (int i = 0; i < n; i++) {
                            a[i] = nextInt();
                    }
                    return a;
            }

            long[] nextLongArray(int n) {
                    long a[] = new long[n];
                    for (int i = 0; i < n; i++) {
                            a[i] = nextInt();
                    }
                    return a;
            }

            String readString() {
                    int c = snext();
                    while (isSpaceChar(c)) {
                            c = snext();
                    }
                    StringBuilder res = new StringBuilder();
                    do {
                            res.appendCodePoint(c);
                            c = snext();
                    } while (!isSpaceChar(c));
                    return res.toString();
            }

            String nextLine() {
                    int c = snext();
                    while (isSpaceChar(c))
                            c = snext();
                    StringBuilder res = new StringBuilder();
                    do {
                            res.appendCodePoint(c);
                            c = snext();
                    } while (!isEndOfLine(c));
                    return res.toString();
            }

            boolean isSpaceChar(int c) {
                    if (filter != null)
                            return filter.isSpaceChar(c);
                    return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
            }

            private boolean isEndOfLine(int c) {
                    return c == '\n' || c == '\r' || c == -1;
            }

            interface SpaceCharFilter {
                    boolean isSpaceChar(int ch);
            }
    }
}    

