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 s, t;
long a[26], b[26];
int main() {
  ios_base::sync_with_stdio(false);
  cin >> s;
  cin >> t;
  long n, i, j, k;
  n = s.size();
  char ans[n + 1];
  for (i = 0; i < n; i++) {
    a[s[i] - 'a']++;
    b[t[i] - 'a']++;
  }
  j = 0;
  k = 25;
  while (b[k] == 0) k--;
  while (a[j] == 0) j++;
  for (i = 0; i < n; i++) {
    if (i % 2 == 0) {
      while (a[j] == 0) j++;
      if (j <= k)
        ans[i] = char('a' + j);
      else
        break;
      a[j]--;
    } else {
      while (b[k] == 0) k--;
      if (k >= j)
        ans[i] = char('a' + k);
      else
        break;
      b[k]--;
    }
  }
  long f = i;
  string x = "", y = "";
  char cc;
  for (i; i < n; i++) {
    if (i % 2 == 0) {
      while (a[j] == 0) j++;
      cc = char('a' + j);
      x = cc + x;
      a[j]--;
    } else {
      while (b[k] == 0) k--;
      cc = char('a' + k);
      y = cc + y;
      b[k]--;
    }
  }
  j = 0;
  k = 0;
  for (i = f; i < n; i++) {
    if (i % 2 == 0) {
      ans[i] = x[j];
      j++;
    } else {
      ans[i] = y[k];
      k++;
    }
  }
  for (i = 0; i < n; i++) cout << ans[i];
  return 0;
}
