#include <bits/stdc++.h>
using namespace std;
const int maxn = 3e5 + 10;
string s1;
string s2;
char ans[maxn];
bool cmp(char a, char b) { return a > b; }
int main() {
  cin >> s1;
  cin >> s2;
  int len = s1.size();
  int head = 0;
  int tail = len - 1;
  int head_1 = 0;
  int tail_1 = (len / 2) + (len % 2) - 1;
  int head_2 = 0;
  int tail_2 = len / 2 - 1;
  sort(s1.begin(), s1.end());
  sort(s2.begin(), s2.end(), cmp);
  int cou = len;
  int button = 1;
  while (head <= tail) {
    if (button % 2) {
      if (s1[head_1] < s2[head_2]) {
        ans[head] = s1[head_1];
        head++;
        head_1++;
      } else {
        ans[tail] = s1[tail_1];
        tail--;
        tail_1--;
      }
    } else {
      if (s1[head_1] < s2[head_2]) {
        ans[head] = s2[head_2];
        head++;
        head_2++;
      } else {
        ans[tail] = s2[tail_2];
        tail--;
        tail_2--;
      }
    }
    button++;
  }
  printf("%s\n", ans);
  return 0;
}
