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 a[300010];
char b[300010];
char c[300010];
bool cmp(char a, char b) { return a > b; }
int main() {
  scanf("%s", a);
  scanf("%s", b);
  int n = strlen(a);
  for (int i = 0; i < n; i++) c[i] = '\0';
  sort(a, a + n);
  sort(b, b + n, cmp);
  int l = 0, r = n - 1;
  int al = 0, ar = (n + 1) / 2 - 1;
  int bl = 0, br = n / 2 - 1;
  for (int i = 0; i < n; i++) {
    if (i % 2 == 0) {
      if (a[al] >= b[bl]) {
        c[r] = a[ar];
        r--;
        ar--;
      } else {
        c[l] = a[al];
        l++;
        al++;
      }
    } else {
      if (b[bl] <= a[al]) {
        c[r] = b[br];
        r--;
        br--;
      } else {
        c[l] = b[bl];
        l++;
        bl++;
      }
    }
  }
  c[n] = '\0';
  printf("%s", c);
  return 0;
}
