#include <bits/stdc++.h>
using namespace std;
int main() {
  string a, b;
  cin >> a >> b;
  sort(a.begin(), a.end());
  sort(b.begin(), b.end());
  string s = "", t = "";
  int sz = a.size();
  int la = 0, ra = sz % 2 ? sz / 2 : sz / 2 - 1;
  int lb = sz - sz / 2, rb = sz - 1;
  for (int i = 0; i < sz; i++) {
    if (i % 2 == 0) {
      if (a[la] < b[rb])
        s += a[la++];
      else
        t += a[ra--];
    } else {
      if (b[rb] <= a[la])
        t += b[lb++];
      else
        s += b[rb--];
    }
  }
  reverse(t.begin(), t.end());
  cout << s << t << endl;
  return 0;
}
