#include <bits/stdc++.h>
using namespace std;
int main() {
  string s, t;
  cin >> s >> t;
  sort(s.begin(), s.end());
  sort(t.begin(), t.end());
  reverse(t.begin(), t.end());
  int n = s.size(), i = 0, j = n - 1, k = 0, l = (n + 1) / 2 - 1, m = 0,
      o = n / 2 - 1;
  string ans(n, ' ');
  while (k <= l && m <= o) {
    if (s[k] < t[m]) {
      ans[i++] = s[k++];
    } else {
      ans[j--] = s[l--];
    }
    if (t[m] > s[k]) {
      ans[i++] = t[m++];
    } else {
      ans[j--] = t[o--];
    }
  }
  if (k <= l) ans[i] = s[k];
  cout << ans << endl;
}
