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;
bool comp(int x, int y) { return x > y; }
int main() {
  string s1, s2;
  cin >> s1 >> s2;
  int n = s1.size();
  vector<int> v1, v2;
  int i;
  for (i = 0; i < n; i++) {
    int x;
    x = s1[i] - 'a';
    v1.push_back(x);
    x = s2[i] - 'a';
    v2.push_back(x);
  }
  sort(v1.begin(), v1.end());
  sort(v2.begin(), v2.end(), comp);
  string s = "";
  int i1 = 0, i2 = 0;
  int x = 0;
  for (i = 0; i < n; i++)
    if (v1[i] < v2[i]) x++;
  int in = 0;
  int mn = min(((x * 2) - 1), n - 1);
  for (int i = 0; i <= mn; i += 2) {
    cout << char(v1[in] + 'a');
    if (i + 1 < n) cout << char(v2[in] + 'a');
    in++;
  }
  for (int i = mn + 1; i < n; i += 2) {
    if (i >= n - 1) {
      cout << char(v1[in] + 'a');
    } else {
      cout << char(v2[in] + 'a') << char(v1[in] + 'a');
    }
    in++;
  }
}
