#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  ;
  long long precision = numeric_limits<long double>::digits10;
  ;
  string s1, s2;
  cin >> s1 >> s2;
  int n;
  n = s1.size();
  vector<char> s(n, 'a'), t(n, 'a');
  for (long long i = 0; i < n; i++) s[i] = s1[i];
  for (long long i = 0; i < n; i++) t[i] = s2[i];
  string ans(n, '?');
  sort(s.begin(), s.end());
  sort(t.begin(), t.end());
  int l = 0, r = n - 1, rem = n;
  for (long long i = 0; i < n; i++) {
    if (i % 2 == 0) {
      if (s[l] < t[r]) {
        ans[i] = s[l];
        l++;
      } else {
        while (true) {
          if (rem == 0) break;
          if (rem % 2 == 0) {
            ans[i] = t[r];
            r--;
            i++;
          } else {
            ans[i] = s[l];
            l++;
            i++;
          }
          rem--;
        }
        break;
      }
      rem -= 1;
    } else {
      if (t[r] > s[l]) {
        ans[i] = t[r];
        r--;
      } else {
        while (true) {
          if (rem == 0) break;
          if (rem % 2 == 1) {
            ans[i] = t[r];
            r--;
            i++;
          } else {
            ans[i] = s[l];
            l++;
            i++;
          }
          rem--;
        }
        break;
      }
      rem -= 1;
    }
  }
  cout << ans << endl;
}
