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;
char s1[300005], s2[300005], s3[300005];
bool r1(char a, char b) { return (a <= b); }
bool r2(char a, char b) { return (a >= b); }
int main() {
  cin >> s1;
  cin >> s2;
  int n = strlen(s1), x1 = 0, x2 = n - 1, a1 = 0, a2 = (n + 1) / 2 - 1, b1 = 0,
      b2 = n / 2 - 1;
  sort(s1, s1 + n, r1);
  sort(s2, s2 + n, r2);
  for (int i = 0; i < n; i++) {
    if (i % 2 == 0) {
      if (s1[a1] < s2[b2]) {
        s3[x1++] = s1[a1++];
      } else {
        s3[x2--] = s1[a2--];
      }
    } else {
      if (s1[a1] < s2[b2]) {
        s3[x1++] = s2[b1++];
      } else {
        s3[x2--] = s2[b2--];
      }
    }
  }
  s3[n] = '\0';
  cout << s3;
  return 0;
}
