#include <bits/stdc++.h>
using namespace std;
const int N = 6e5 + 20;
const double eps = 1e-10;
char a[N], b[N];
char s[N];
int main() {
  while (scanf("%s%s", a + 1, b + 1) != EOF) {
    memset(s, 0, sizeof(s));
    int n = strlen(a + 1);
    sort(a + 1, a + n + 1);
    sort(b + 1, b + n + 1);
    reverse(b + 1, b + 1 + n);
    int p1 = 1, q1 = n / 2;
    int p2 = 1, q2 = n / 2;
    if (n % 2) q1++;
    int i = 1, l = 1, r = n;
    while (l <= r) {
      if (i % 2) {
        if (a[p1] < b[p2])
          s[l++] = a[p1++];
        else
          s[r--] = a[q1--];
      } else {
        if (b[p2] > a[p1])
          s[l++] = b[p2++];
        else
          s[r--] = b[q2--];
      }
      i++;
    }
    printf("%s\n", s + 1);
  }
  return 0;
}
