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 main() {
  int n, i, j, k, la, ra, lb, rb, x, y, z;
  string a, b, c;
  int ca[26], cb[26];
  for (i = 0; i < 26; i++) {
    ca[i] = cb[i] = 0;
  }
  cin >> a >> b;
  n = a.size();
  c = a;
  for (i = 0; i < n; i++) {
    ca[a[i] - 'a']++;
    cb[b[i] - 'a']++;
  }
  x = 0, y = 0;
  for (i = 0; i < 26; i++) {
    while (ca[i]) {
      a[x++] = i + 'a';
      ca[i]--;
    }
    while (cb[25 - i]) {
      b[y++] = (25 - i) + 'a';
      cb[25 - i]--;
    }
  }
  la = 0, ra = (n + 1) / 2 - 1, lb = 0, rb = n / 2 - 1;
  x = 0, y = n - 1;
  for (i = 0; i < n; i++) {
    if (i % 2 == 0) {
      if (a[la] < b[lb]) {
        c[x++] = a[la++];
      } else if (a[la] >= b[lb]) {
        c[y--] = a[ra--];
      }
    } else {
      if (a[la] < b[lb]) {
        c[x++] = b[lb++];
      } else if (a[la] >= b[lb]) {
        c[y--] = b[rb--];
      }
    }
  }
  cout << c << endl;
}
