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

bccdb
 z
 dfdeed
 aab
 y
 abac

#include <bits/stdc++.h>
using namespace std;
string str1, str2;
int len, loc, len1, len2;
char sma = 'a', lar = 'z';
char str[300002];
int main() {
  cin >> str1 >> str2;
  len1 = len2 = len = str1.length();
  for (int a = 0; a < len1; a++) {
    if (loc * 2 >= len) {
      loc = 0;
      break;
    }
    if (str1[a] == sma) {
      str1.erase(a, 1);
      str[loc * 2] = sma;
      loc++;
      len1--;
      a--;
    }
    if (a == len1 - 1) {
      sma = char(sma + 1);
      a = -1;
    }
  }
  for (int b = 0; b < len2; b++) {
    if (loc * 2 + 1 >= len) break;
    if (str2[b] == lar) {
      str2.erase(b, 1);
      str[loc * 2 + 1] = lar;
      loc++;
      len2--;
      b--;
    }
    if (b == len2 - 1) {
      lar = char(lar - 1);
      b = -1;
    }
  }
  cout << str;
  return 0;
}
