#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  string s1, s2;
  cin >> s1 >> s2;
  long long n = s1.length();
  char answer[n];
  sort(s1.begin(), s1.end());
  sort(s2.begin(), s2.end());
  reverse(s2.begin(), s2.end());
  long long sta = 0;
  long long last = n - 1;
  long long s1p = 0;
  long long s2pl = (n) / 2;
  long long s1pl = (n + 1) / 2;
  s2pl--;
  s1pl--;
  long long s2p = 0;
  long long lastused1 = s1[0];
  long long lastused2 = s2[0];
  for (long long i = 0; i < n; i++) {
    if (i & 1 == 1) {
      if (s1[s1p] < s2[s2p]) {
        answer[sta] = s2[s2p];
        sta++;
        s2p++;
        lastused2 = s2[s2p];
      } else {
        answer[last] = s2[s2pl];
        last--;
        s2pl--;
      }
    } else {
      if (s1[s1p] < s2[s2p]) {
        answer[sta] = s1[s1p];
        sta++;
        s1p++;
        lastused1 = s1[s1p];
      } else {
        answer[last] = s1[s1pl];
        last--;
        s1pl--;
      }
    }
  }
  for (long long i = 0; i < n; i++) cout << answer[i];
  return 0;
}
