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 = 300005;
char A[MAXN], B[MAXN], C[MAXN];
int n;
int main() {
  scanf("%s%s", A, B);
  n = strlen(A);
  sort(A, A + n);
  sort(B, B + n);
  reverse(B, B + n);
  int pa = 0, pb = 0, ra = 0, rb = 0, l = 0, r = n - 1;
  for (int i = 1; i <= n; i++)
    if (i & 1)
      ra++;
    else
      rb++;
  bool ca = 0, cb = 0;
  for (int i = 1; i <= n; i++) {
    if (i & 1) {
      if (A[pa] < B[pb] && !ca)
        C[l++] = A[pa++];
      else {
        ca = cb = 1;
        C[r--] = A[--ra];
      }
    } else {
      if (B[pb] > A[pa] && !cb)
        C[l++] = B[pb++];
      else {
        ca = cb = 1;
        C[r--] = B[--rb];
      }
    }
  }
  for (int i = 0; i < n; i++) printf("%c", C[i]);
  putchar('\n');
  return 0;
}
