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 s1[300005];
char s2[300005];
char ans[300005];
bool cmp1(char s1, char s2) { return s1 < s2; }
bool cmp2(char s1, char s2) { return s1 > s2; }
int n;
int main() {
  cin >> s1 >> s2;
  n = strlen(s1);
  sort(s1, s1 + n, cmp1);
  sort(s2, s2 + n, cmp2);
  int L = 0, R = n - 1;
  int l1 = 0, l2 = 0;
  int r1 = (n + 1) / 2 - 1, r2 = n / 2 - 1;
  int flag = 0;
  for (int i = 0; i < n; i++) {
    if (s1[l1] >= s2[l2]) flag = 1;
    if (i % 2 == 0) {
      if (!flag) {
        ans[L] = s1[l1];
        L++;
        l1++;
      } else {
        ans[R] = s1[r1];
        R--;
        r1--;
      }
    } else {
      if (!flag) {
        ans[L] = s2[l2];
        L++;
        l2++;
      } else {
        ans[R] = s2[r2];
        R--;
        r2--;
      }
    }
  }
  for (int i = 0; i < n; i++) {
    cout << ans[i];
  }
  return 0;
}
