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 cmp(char a, char b) { return a > b; }
int main() {
  char s1[3 * 100001];
  char s2[3 * 100001];
  char s3[3 * 100001];
  scanf("%s%s", s1, s2);
  int len = strlen(s1);
  sort(s1, s1 + len);
  sort(s2, s2 + len, cmp);
  int n = 0;
  int n1 = 0, n2 = 0;
  while (n < len) {
    if (s1[n] < s2[n]) {
      if (n % 2 == 0)
        s3[n++] = s1[n1++];
      else
        s3[n++] = s2[n2++];
    } else {
      if (n % 2 == 0)
        s3[n++] = s2[n1++];
      else
        s3[n++] = s1[n2++];
    }
  }
  printf("%s\n", s3);
}
