#include <bits/stdc++.h>
using namespace std;
string a, b;
int idx, idx2, fin1, fin2;
char r[400002];
int fin, in;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cin >> a >> b;
  int n = a.size();
  fin = n - 1;
  fin1 = (n + 1) / 2 - 1;
  fin2 = (n) / 2 - 1;
  sort(a.begin(), a.end());
  sort(b.begin(), b.end());
  reverse(b.begin(), b.end());
  for (int i = 0; i < n; i++) {
    if (i % 2 == 0) {
      if (a[idx] < b[idx2])
        r[in++] = a[idx++];
      else {
        r[fin--] = a[fin1--];
      }
    } else {
      if (b[idx2] > a[idx])
        r[in++] = b[idx2++];
      else {
        r[fin--] = b[fin2--];
      }
    }
  }
  for (int i = 0; i < n; i++) {
    cout << r[i];
  }
  cout << "\n";
}
