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[300005], b[300005], c[300005];
bool big(char a, char b) { return a > b; }
int main() {
  cin >> a >> b;
  int l = strlen(a), l1 = 0, l2 = 0, r1 = (l + 1) / 2 - 1, r2 = l / 2 - 1,
      l3 = 0, r = l - 1;
  sort(a, a + l);
  sort(b, b + l, big);
  for (int i = 0; i < l; i++) {
    if (i & 1) {
      if (a[l1] < b[l2]) {
        c[l3] = b[l2];
        l3++;
        l2++;
      } else {
        c[r] = b[r2];
        r--;
        r2--;
      }
    } else {
      if (a[l1] < b[l2]) {
        c[l3] = a[l1];
        l3++;
        l1++;
      } else {
        c[r] = a[r1];
        r--;
        r1--;
      }
    }
  }
  cout << c;
  return 0;
}
