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 = 300000 + 50;
const int INF = 1 << 30;
char s[MAXN], t[MAXN];
char ans[MAXN];
int main() {
  scanf("%s%s", s, t);
  int len = strlen(s);
  sort(s, s + len);
  sort(t, t + len);
  int cnts = 0, cntt = len - 1, flag = 0, ch = 0;
  for (int i = 0; i < len; ++i) {
    if (!ch && s[cnts] >= t[cntt]) {
      flag = !((len % 2) ^ (i % 2));
      ch = 1;
    }
    if ((i + flag) % 2) {
      ans[i] = t[cntt--];
    } else
      ans[i] = s[cnts++];
  }
  ans[len] = '\0';
  printf("%s\n", ans);
  return 0;
}
