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

bccdb
 z
 dfdeed
 aab
 y
 abac

#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:10240000000,10240000000")
using namespace std;
char ss[300005], tt[300005];
int main() {
  while (scanf("%s%s", ss, tt) != EOF) {
    string s(ss);
    string t(tt);
    sort(s.begin(), s.end());
    sort(t.begin(), t.end());
    reverse(t.begin(), t.end());
    deque<char> a, b;
    int n = s.size();
    for (int i = 0; i < (n + 1) / 2; i++) {
      a.push_back(s[i]);
    }
    for (int i = 0; i < (n) / 2; i++) {
      b.push_back(t[i]);
    }
    string res1 = "", res2 = "";
    for (int i = 0; i < n; i++) {
      if (i % 2 == 0) {
        if (!b.empty() && a[0] >= b[0]) {
          res2 += a.back();
          a.pop_back();
        } else {
          res1 += a[0];
          a.pop_front();
        }
      } else {
        if (!a.empty() && b[0] <= a[0]) {
          res2 += b.back();
          b.pop_back();
        } else {
          res1 += b[0];
          b.pop_front();
        }
      }
    }
    reverse(res2.begin(), res2.end());
    cout << res1 + res2 << endl;
  }
  return 0;
}
