#include <bits/stdc++.h>
using namespace std;
const int maxn = 3e5 + 10;
char str1[maxn], str2[maxn];
char str[maxn];
int n;
int main() {
  while (cin >> str1 >> str2) {
    n = strlen(str1);
    sort(str1, str1 + n);
    sort(str2, str2 + n);
    reverse(str2, str2 + n);
    int len = n;
    int Alen = (n + 1) / 2 - 1;
    int Blen = (n) / 2 - 1;
    int Begin = 0;
    int last = n - 1;
    int Acnt1 = 0;
    int Bcnt1 = 0;
    for (int i = 1; i <= n; i++) {
      if (i & 1) {
        if (str1[Acnt1] < str2[Bcnt1]) {
          str[Begin++] = str1[Acnt1++];
        } else {
          str[last--] = str1[Alen--];
        }
      } else {
        if (str2[Bcnt1] > str1[Acnt1]) {
          str[Begin++] = str2[Bcnt1++];
        } else {
          str[last--] = str2[Blen--];
        }
      }
    }
    str[n] = '\0';
    cout << str << endl;
  }
  return 0;
}
