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;
const int maxn = 3e5 + 10;
char a[maxn], b[maxn], c[maxn];
int main() {
  while (scanf("%s%s", a, b) != EOF) {
    int len = strlen(a);
    sort(a, a + len);
    sort(b, b + len, greater<char>());
    int apos = 0;
    int bpos = 0;
    int apos2 = len / 2 - 1;
    int bpos2 = len / 2 - 1;
    if (len % 2 != 0) {
      apos2++;
    }
    bool achoose = true;
    int st = 0;
    for (st = 0; st < len; st++) {
      if (a[apos] >= b[bpos]) {
        break;
      }
      if (achoose) {
        c[st] = a[apos++];
        achoose = false;
      } else {
        c[st] = b[bpos++];
        achoose = true;
      }
    }
    apos = len / 2 - 1;
    bpos = len / 2 - 1;
    for (int i = len - 1; i >= st; i--) {
      if (achoose) {
        c[i] = a[apos2--];
        achoose = false;
      } else {
        c[i] = b[bpos2--];
        achoose = true;
      }
    }
    for (int i = 0; i < len; i++) {
      printf("%c", c[i]);
    }
    printf("\n");
  }
  return 0;
}
