#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  string s[2];
  cin >> s[0] >> s[1];
  string c = s[0];
  sort(s[0].begin(), s[0].end());
  sort(s[1].begin(), s[1].end(), greater<char>());
  int n = s[0].size();
  int end = n - 1;
  int oi[2];
  oi[0] = n / 2 + n % 2 - 1;
  oi[1] = n / 2 - 1;
  for (int i = 0; i < n; i++) {
    if (s[0][i / 2 + i % 2] < s[1][i / 2]) {
      c[i] = s[i % 2][i / 2];
    } else {
      c[end] = s[i % 2][oi[i % 2]];
      end--;
      oi[i % 2]--;
    }
  }
  cout << c;
  return 0;
}
