bcdef
abbbc
 z
y
 reddit
abcdef
 abc
aaa
 y
z
 cbxz
aaaa

bccdb
 z
 dfdeed
 aab
 y
 abac

#include <bits/stdc++.h>
char a[300002], b[300002], c[300002];
int main() {
  scanf("%s%s", a, b);
  int n = strlen(a), ca = 0, cb = 0;
  std::sort(a, a + n);
  std::sort(b, b + n);
  std::reverse(b, b + n);
  int i;
  for (i = 0; i < n; i++)
    if (~i & 1) {
      if (a[ca] > b[cb]) break;
      c[i] = a[ca++];
    } else {
      if (b[cb] < a[ca]) break;
      c[i] = b[cb++];
    }
  int t = i;
  for (; i < t + (n - t) / 2; i++) {
    c[i] = b[cb++];
  }
  for (t = n - 1; t >= i; --t) c[t] = a[ca++];
  c[n] = 0;
  printf("%s", c);
  return 0;
}
