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 C[300004], D[300004];
int CC[500], DD[500];
int idx1, idx2, len, idx3, idx4, idx5, idx6;
char q1[300004], q2[300004];
char Ans[300004];
int main() {
  scanf("%s%s", C, D);
  for (len = 0; C[len] != NULL; len++)
    ;
  sort(C, C + len);
  sort(D, D + len);
  for (int i = 1; i <= (len + 1) / 2; i++) q1[i] = C[i - 1];
  for (int i = 1; i <= len / 2; i++) q2[len / 2 - i + 1] = D[len - i];
  idx1 = idx3 = 1;
  idx2 = (len + 1) / 2;
  idx4 = len / 2;
  idx5 = 1;
  idx6 = len;
  for (int i = 1; i <= len; i++) {
    if (i & 1) {
      if (q1[idx1] < q2[idx4])
        Ans[idx5++] = q1[idx1++];
      else
        Ans[idx6--] = q1[idx2--];
    } else {
      if (q2[idx4] > q1[idx1])
        Ans[idx5++] = q2[idx4--];
      else
        Ans[idx6--] = q2[idx3++];
    }
  }
  printf("%s", Ans + 1);
}
