#include <bits/stdc++.h>
using namespace std;
int N;
string S, T, ans;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cin >> S >> T;
  N = (int)S.size();
  sort(S.begin(), S.end());
  sort(T.begin(), T.end());
  reverse(T.begin(), T.end());
  ans.resize(N);
  int as = 0, bs = (N + 1) / 2, at = 0, bt = N / 2;
  int a = 0, b = N;
  for (int i = 0; i < N; i++) {
    if (i % 2 == 0) {
      if (S[as] < T[at])
        ans[a++] = S[as++];
      else
        ans[--b] = S[--bs];
    } else {
      if (T[at] > S[as])
        ans[a++] = T[at++];
      else
        ans[--b] = T[--bt];
    }
  }
  cout << ans << "\n";
  return 0;
}
