#include <bits/stdc++.h>
using namespace std;
const int mod = 1000000000 + 7;
int addm(int& a, int b) { return (a += b) < mod ? a : a -= mod; }
template <class T, class U>
bool smin(T& a, U b) {
  return a > b ? (a = b, 1) : 0;
}
template <class T, class U>
bool smax(T& a, U b) {
  return a < b ? (a = b, 1) : 0;
}
int n;
string s1, s2;
string r;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cin >> s1 >> s2;
  n = s1.size();
  int ct = 0;
  r.resize(n);
  sort(s1.begin(), s1.end());
  sort(s2.rbegin(), s2.rend());
  int i = 0, j = (n + 1) / 2, k = 0, l = n / 2;
  while (1) {
    if (ct == n) break;
    if (k == n) break;
    if (s1[i] >= s2[k]) break;
    r[ct++] = s1[i++];
    if (ct == n) break;
    if (i == n) break;
    if (s1[i] >= s2[k]) break;
    r[ct++] = s2[k++];
  }
  int ct2 = n - 1;
  bool turn = ct % 2;
  while (ct2 >= ct) {
    if (!turn) {
      r[ct2--] = s1[--j];
    } else
      r[ct2--] = s2[--l];
    turn = !turn;
  }
  cout << r << endl;
}
