bcdef
abbbc
 z
y
 reddit
abcdef
 abc
aaa
 y
z
 cbxz
aaaa

bccdb
 z
 dfdeed
 aab
 y
 abac

#include <bits/stdc++.h>
using namespace std;
int main() {
  int numa = 0, numb = 25;
  int sa[26], sb[26];
  memset(sa, 0, sizeof(sa));
  memset(sb, 0, sizeof(sb));
  string a, b;
  char ans[300005];
  cin >> a >> b;
  int n = a.length();
  for (int i = 0; i < n; i++) {
    sa[a[i] - 'a']++;
    sb[b[i] - 'a']++;
  }
  for (int i = 0; i < n; i++) {
    char ch;
    if (i % 2) {
      while (1) {
        if (sb[numb]) {
          sb[numb]--;
          ch = (char)'a' + numb;
          break;
        } else
          numb--;
      }
    } else {
      while (1) {
        if (sa[numa]) {
          sa[numa]--;
          ch = (char)'a' + numa;
          break;
        } else
          numa++;
      }
    }
    ans[i] = ch;
  }
  cout << ans << endl;
  return 0;
}
