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;
int n;
int cnt1[N], cnt2[N];
char s[N], t[N];
int main() {
  scanf("%s%s", s + 1, t + 1);
  n = strlen(s + 1);
  for (int i = 1; i <= n; ++i) ++cnt1[s[i] - 'a'];
  for (int i = 1; i <= n; ++i) ++cnt2[t[i] - 'a'];
  int pos1 = 0, pos2 = 25;
  for (int i = 1; i <= n; ++i) {
    while (cnt1[pos1] == 0) ++pos1;
    while (cnt2[pos2] == 0) --pos2;
    if (i % 2 == 1)
      printf("%c", (char)(pos1 + 'a')), --cnt1[pos1];
    else
      printf("%c", (char)(pos2 + 'a')), --cnt2[pos2];
  }
  return 0;
}
