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;
void advance(string &s, int &ind, int rev) {
  while (ind >= 0 && ind < s.size() && s[ind] != '.') ind += rev;
}
int main() {
  string s[2];
  cin >> s[0] >> s[1];
  int n = s[0].size();
  sort(s[0].begin(), s[0].end());
  sort(s[1].rbegin(), s[1].rend());
  string res(n, '.');
  int ind0s = 0, ind1s = 0, ind0e = (n + 1) / 2 - 1, ind1e = n / 2 - 1;
  int inds = 0, inde = n - 1;
  for (int i = 0; i < n; i++) {
    if (i % 2 == 0) {
      if (s[1][ind1s] > s[0][ind0s]) {
        advance(res, inds, 1);
        res[inds] = s[0][ind0s];
        ind0s++;
      } else {
        advance(res, inde, -1);
        res[inde] = s[0][ind0e];
        ind0e--;
      }
    } else {
      if (s[0][ind0s] < s[1][ind1s]) {
        advance(res, inds, 1);
        res[inds] = s[1][ind1s];
        ind1s++;
      } else {
        advance(res, inde, -1);
        res[inde] = s[1][ind1e];
        ind1e--;
      }
    }
  }
  cout << res << endl;
  return 0;
}
