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

bccdb
 z
 dfdeed
 aab
 y
 abac

import java.util.Arrays;
import java.util.Scanner;

/**
 * Created by mostafa on 5/18/17.
 */
public class R414C {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        char[] oleg = sc.nextLine().toCharArray();
        char[] igor = sc.nextLine().toCharArray();
        int n = oleg.length;

        int remOleg = (n + 1) / 2;
        int remIgor = n / 2;

        Arrays.sort(oleg);
        Arrays.sort(igor);
        reverse(igor);

        int olegLeft = 0, olegRight = n - remOleg;
        int igorLeft = 0, igorRight = n - remIgor;

        int left = 0;
        int right = oleg.length - 1;

        char[] res = new char[right + 1];

        int turn = 0;
        while(left <= right) {
            if(turn == 0) {
                if(oleg[olegLeft] >= igor[igorLeft]) {
                    res[right--] = oleg[olegRight--];
                }
                else
                    res[left++] = oleg[olegLeft++];
            }
            else {
                if(igor[igorLeft] <= oleg[olegLeft])
                    res[right--] = igor[igorRight--];
                else
                    res[left++] = igor[igorLeft++];
            }

            turn = 1 - turn;
        }

        System.out.println(new String(res));
    }

    static void reverse(char[] x) {
        for(int i = 0; i < x.length / 2; i++) {
            char tmp = x[i];
            x[i] = x[x.length - i - 1];
            x[x.length - i - 1] = tmp;
        }

    }
}
