#include <bits/stdc++.h>
char A[300010], B[300010], Ans[300010];
int a, b, len, ra, la, rb, lb, lA, rA;
bool cmp(char i, char j) { return i > j; }
int main() {
  scanf("%s %s", A, B);
  for (; A[a] != '\0'; a++)
    ;
  for (; B[b] != '\0'; b++)
    ;
  len = (a < b ? a : b);
  std::sort(A, A + a);
  std::sort(B, B + b, cmp);
  rb = len >> 1;
  ra = len - rb;
  rA = len - 1;
  rb--, ra--;
  for (register int i = 0; i < len; i++) {
    if (i & 1) {
      if (B[lb] <= A[la])
        Ans[rA--] = B[rb--];
      else
        Ans[lA++] = B[lb++];
    } else {
      if (A[la] >= B[lb])
        Ans[rA--] = A[ra--];
      else
        Ans[lA++] = A[la++];
    }
  }
  printf("%s", Ans);
  return 0;
}
