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

bccdb
 z
 dfdeed
 aab
 y
 abac

#include <bits/stdc++.h>
const int MAXINT = 2147483640;
const long long MAXLL = 9223372036854775800LL;
const long long MAXN = 1000000;
using namespace std;
string s[2];
int i, n, have[2], to[2], place, now;
char ans[MAXN];
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  srand(time(0));
  cin >> s[1] >> s[0];
  sort(s[1].begin(), s[1].end());
  sort(s[0].begin(), s[0].end());
  reverse(s[0].begin(), s[0].end());
  n = s[1].size();
  place = 1;
  now = 1;
  while (place <= n && s[1][to[1]] < s[0][to[0]]) {
    ans[place++] = s[now][to[now]++];
    now = 1 - now;
  }
  now = n % 2;
  while (place <= n) {
    ans[place++] = s[now][to[now]++];
    now = 1 - now;
  }
  for (i = 1; i <= n; i++) cout << ans[i];
  return 0;
}
