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;
const int maxn = 100005;
int n, p1, p2;
string s, t, ans;
int main() {
  ios_base::sync_with_stdio(false);
  cin >> s >> t;
  sort(s.begin(), s.end());
  sort(t.begin(), t.end());
  ans.resize(s.length(), 0);
  p1 = 0;
  p2 = (int)s.length() - 1;
  n = (int)s.length() - 1;
  for (int i = 0; i <= n; ++i) {
    if (t[p2] <= s[p1]) {
      if (i % 2 == 0)
        ans[n] = s[p1++];
      else
        ans[n] = t[p2--];
      n -= 1;
    } else {
      if (i % 2 == 0)
        ans[i] = s[p1++];
      else
        ans[i] = t[p2--];
    }
  }
  cout << ans;
  return 0;
}
