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#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:256000000")
using namespace std;
const long double PI = 3.14159265358979323846;
const long double gammama = 0.57721566490153286060;
const long double eps = 1e-5;
const int INF = 1000 * 1000 * 1000 + 1;
const long long LINF = (long long)1000 * 1000 * 1000 * 1000 * 1000 * 1000;
const long long mod = 1000 * 1000 * 1000 + 7;
const long long N = 1001;
void solve() {
  string s1, s2;
  cin >> s1 >> s2;
  sort(s1.begin(), s1.end());
  sort(s2.rbegin(), s2.rend());
  int n = s1.size();
  int n1 = (n + 1) / 2, n2 = n / 2;
  s1.resize(n1);
  s2.resize(n2);
  string res;
  res.resize(n);
  int i1 = 0, i2 = 0, i = 0;
  while (i < n) {
    if (i % 2 == 0) {
      if (s1[i1] < s2[i2]) {
        res[i] = s1[i1];
        ++i;
        ++i1;
      } else {
        break;
      }
    } else {
      if (s2[i2] > s1[i1]) {
        res[i] = s2[i2];
        ++i;
        ++i2;
      } else {
        break;
      }
    }
  }
  int j = n - 1, j1 = n1 - 1, j2 = n2 - 1;
  while (j >= i) {
    if ((i + n - 1 - j) % 2 == 0) {
      res[j] = s1[j1];
      --j;
      --j1;
    } else {
      res[j] = s2[j2];
      --j;
      --j2;
    }
  }
  cout << res << endl;
}
int main() {
  ios_base::sync_with_stdio(0);
  solve();
  return 0;
}
