#include <bits/stdc++.h>
using namespace std;
int main() {
  std::ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  string s1, s2, a, b, ans;
  cin >> s1 >> s2;
  sort(s1.begin(), s1.end());
  sort(s2.begin(), s2.end(), greater<char>());
  int n, n1, n2, p = 0, q = 0, r = 0, u, v, w;
  n = s1.length();
  if (n & 1) {
    n1 = n / 2 + 1;
    n2 = n / 2;
  } else {
    n1 = n / 2;
    n2 = n1;
  }
  u = n1 - 1;
  v = n2 - 1;
  w = n - 1;
  for (int i = 0; i < n1; i++) a += s1[i];
  for (int i = 0; i < n2; i++) b += s2[i];
  for (int i = 0; i < n; i++) ans += '?';
  for (int i = 0; i < n; i++) {
    if (!(i & 1)) {
      if (a[p] >= b[q])
        ans[w--] = a[u--];
      else
        ans[r++] = a[p++];
    } else {
      if (a[p] >= b[q])
        ans[w--] = b[v--];
      else
        ans[r++] = b[q++];
    }
  }
  cout << ans;
  return 0;
}
