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;
char ans[300001];
int main() {
  string S1, S2;
  cin >> S1 >> S2;
  sort(S1.begin(), S1.end());
  sort(S2.begin(), S2.end());
  int a = 0;
  int b = S2.size() - 1;
  int x = S2.size() - 1;
  for (int i = 0; i < S1.size(); i++) {
    if (i % 2 == 0) {
      if (S1[a] < S2[b]) {
        ans[i] = S1[a];
        a++;
      } else {
        ans[x] = S1[a];
        a++;
        x--;
      }
    } else {
      if (S2[b] > S1[a]) {
        ans[i] = S2[b];
        b--;
      } else {
        ans[x] = S2[b];
        b--;
        x--;
      }
    }
  }
  cout << ans << endl;
}
