#include <bits/stdc++.h>
#pragma GCC optimize("O3")
using namespace std;
long long mod = 1e9 + 7;
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  string s1, s2;
  cin >> s1 >> s2;
  sort(s1.begin(), s1.end());
  sort(s2.begin(), s2.end(), greater<char>());
  long long i = 0, j = 0, f = 0, n = s1.size(), cnt = 0;
  string ans("");
  while (cnt < n) {
    if (!f) {
      if (s1[i] >= s2[j]) break;
      ans += s1[i++];
    } else {
      if (s2[j] <= s1[i]) break;
      ans += s2[j++];
    }
    ++cnt;
    f ^= 1;
  }
  if (cnt < n) {
    long long p = n - cnt;
    if (p % 2 == 0) f ^= 1;
    while (cnt < n) {
      if (!f)
        ans += s1[i++];
      else
        ans += s2[j++];
      ++cnt;
      f ^= 1;
    }
  }
  cout << ans;
  return 0;
}
