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;
int cnt[2][26];
char ss[30005];
int main() {
  int n;
  scanf("%s", ss);
  n = strlen(ss);
  int cur = 0;
  for (int i = 0; i < n; i++) {
    cnt[cur][ss[i] - 'a']++;
  }
  cur = 1;
  scanf("%s", ss);
  for (int i = 0; i < n; i++) {
    cnt[cur][ss[i] - 'a']++;
  }
  cur = 0;
  for (int i = 0; i < n; i++) {
    char ch;
    if (!cur) {
      for (int i = 0; i < 26; i++) {
        if (cnt[cur][i]) {
          ch = i + 'a';
          cnt[cur][i]--;
          break;
        }
      }
    } else {
      for (int i = 25; i >= 0; i--) {
        if (cnt[cur][i]) {
          ch = i + 'a';
          cnt[cur][i]--;
          break;
        }
      }
    }
    putchar(ch);
    cur ^= 1;
  }
  puts("");
  return 0;
}
