bcdef
abbbc
 z
y
 reddit
abcdef
 abc
aaa
 y
z
 cbxz
aaaa

bccdb
 z
 dfdeed
 aab
 y
 abac

#include <bits/stdc++.h>
using namespace std;
int main() {
  vector<char> O, I;
  string ol, ig;
  int flag = 0;
  cin >> ol;
  cin >> ig;
  int l, set = 1;
  l = ol.length();
  char final[l];
  int index;
  int j = 0, k = l - 1;
  int ptrE = l - 1, ptrS = 0;
  for (int i = 0; i < l; i++) {
    O.push_back(ol[i]);
    I.push_back(ig[i]);
  }
  std::sort(O.begin(), O.begin() + l);
  std::sort(I.begin(), I.begin() + l);
  for (int i = 0; i < l; i++) {
    if (i % 2 != 0) {
      if (I.at(k) <= O.at(j)) {
        index = (l - i - 1) / 2;
        final[ptrE] = I.at(k - index);
        ptrE--;
      } else {
        final[ptrS] = I.at(k);
        k--;
        ptrS++;
      }
    } else {
      if (O.at(j) >= I.at(k)) {
        index = (l - i - 1) / 2;
        final[ptrE] = O.at(j + index);
        ptrE--;
      } else {
        final[ptrS] = O.at(j);
        j++;
        ptrS++;
      }
    }
  }
  for (int i = 0; i < l; i++) cout << final[i];
  return 0;
}
