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;
const int maxn = 300010;
int n;
char s[maxn], t[maxn], ans[maxn];
int main() {
  scanf("%s %s", s + 1, t + 1), n = strlen(s + 1);
  sort(s + 1, s + n + 1);
  sort(t + 1, t + n + 1);
  int l1 = 1, r1 = n;
  int l2 = 1, r2 = n;
  for (int i = 1, cur = 0; i <= n; i++, cur ^= 1) {
    if (!cur) {
      if (s[l1] < t[r2]) {
        ans[i] = s[l1++];
      } else {
        int cnt = (n + 1) / 2 - i / 2;
        l1 += cnt - 1;
        cnt = n / 2 - (i - 1) / 2;
        r2 -= cnt - 1;
        for (int j = n; j >= i; j--) {
          if (!((n - j) & 1))
            ans[j] = s[l1--];
          else
            ans[j] = t[r2++];
        }
        break;
      }
    } else {
      if (t[r2] > s[l1]) {
        ans[i] = t[r2--];
      } else {
        int cnt = (n + 1) / 2 - i / 2;
        l1 += cnt - 1;
        cnt = n / 2 - (i - 1) / 2;
        r2 -= cnt - 1;
        for (int j = n; j >= i; j--) {
          if (!((n - j) & 1))
            ans[j] = t[r2++];
          else
            ans[j] = s[l1--];
        }
        break;
      }
    }
  }
  printf("%s\n", ans + 1);
  return 0;
}
