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 N = 300010;
bool cmp(char a, char b) { return a > b; }
int main() {
  string s, t;
  char ans[N];
  cin >> s >> t;
  int n = s.length();
  int sl = 0, tl = 0;
  int sr = (n + 1) / 2 - 1, tr = n / 2 - 1;
  int ansl = 0;
  int ansr = s.length() - 1;
  sort(s.begin(), s.end());
  sort(t.begin(), t.end(), cmp);
  for (int i = 0; i < n; i++) {
    if (i % 2 == 0) {
      if (s[sl] >= t[tl])
        ans[ansr--] = s[sr--];
      else
        ans[ansl++] = s[sl++];
    } else {
      if (s[sl] >= t[tl])
        ans[ansr--] = t[tr--];
      else
        ans[ansl++] = t[tl++];
    }
  }
  ans[s.length()] = '\0';
  cout << ans << endl;
  return 0;
}
