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() {
  ios_base::sync_with_stdio(false);
  string s, t;
  cin >> s >> t;
  int n = (int)s.length();
  vector<char> ans(n);
  vector<char> a(n), b(n);
  for (int i = 0; i < n; i++) {
    a[i] = s[i];
    b[i] = t[i];
  }
  sort(a.begin(), a.end());
  sort(b.rbegin(), b.rend());
  int l1 = 0, r1 = 0;
  int l = 0, r = n - 1;
  for (int i = 0; i < n; i++) {
    if (i % 2) {
      if (a[l1] > b[r1]) {
        ans[r] = b[r1];
        r1++;
        r--;
      } else {
        ans[l] = b[r1];
        r1++;
        l++;
      }
    } else {
      if (a[l1] > b[r1]) {
        ans[r] = a[l1];
        l1++;
        r--;
      } else {
        ans[l] = a[l1];
        l1++;
        l++;
      }
    }
  }
  for (int i = 0; i < n; i++) cout << ans[i];
  return 0;
}
