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;
int cmp1(char a, char b) { return a < b; }
int cmp2(char a, char b) { return a > b; }
int main() {
  char a[300005], b[300005], map[300005];
  int n, i, alen1, alen2, blen1, blen2, s, e;
  while (cin >> a >> b) {
    n = strlen(a);
    sort(a, a + n, cmp1);
    sort(b, b + n, cmp2);
    alen1 = 0;
    alen2 = n % 2 == 0 ? n / 2 : n / 2 + 1;
    alen2--;
    blen1 = 0;
    blen2 = n / 2 - 1;
    s = 0, e = n - 1;
    for (i = 0; i < n; i++) {
      if (i % 2 == 0) {
        if (a[alen1] < b[blen1]) {
          map[s++] = a[alen1++];
        } else {
          map[e--] = a[alen2--];
        }
      } else {
        if (b[blen1] > a[alen1]) {
          map[s++] = b[blen1++];
        } else {
          map[e--] = b[blen2--];
        }
      }
    }
    map[n] = '\0';
    cout << map << endl;
  }
  return 0;
}
