#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  string a, b;
  cin >> a >> b;
  int n = a.size();
  sort(a.begin(), a.end());
  sort(b.rbegin(), b.rend());
  char ans[n];
  int l1 = 0, l2 = 0;
  int r1 = (n + 1) / 2 - 1, r2 = n / 2 - 1;
  int l = 0, r = n - 1;
  for (int i = 0; i < n; ++i) {
    if (i % 2 == 0) {
      if (a[l1] < b[l2]) {
        ans[l] = a[l1];
        l++;
        l1++;
      } else {
        ans[r] = a[r1];
        r--;
        r1--;
      }
    } else {
      if (b[l2] > a[l1]) {
        ans[l] = b[l2];
        l++;
        l2++;
      } else {
        ans[r] = b[r2];
        r--;
        r2--;
      }
    }
  }
  for (int i = 0; i < n; ++i) {
    cout << ans[i];
  }
  cout << '\n';
  return 0;
}
