#include <bits/stdc++.h>
using namespace std;
int main() {
  string s, x, z;
  cin >> s >> x;
  sort(s.begin(), s.end());
  sort(x.begin(), x.end());
  z.resize(s.size());
  int n = s.size();
  int a = 0, b = n - 1, c = 0, d = (n - 1) / 2, e = (n + 1) / 2, f = n - 1;
  for (int i = 0; i < s.size(); i++)
    if (i % 2 == 0) {
      if (s[c] < x[f])
        z[a++] = s[c++];
      else
        z[b--] = s[d--];
    } else {
      if (x[f] > s[c])
        z[a++] = x[f--];
      else
        z[b--] = x[e++];
    }
  cout << z;
  return 0;
}
