#include <bits/stdc++.h>
using namespace std;
const int MAX = 300005;
char str1[MAX], str2[MAX], str3[MAX];
int main() {
  scanf("%s %s", str1, str2);
  int n = strlen(str1);
  str3[n] = '\0';
  sort(str1, str1 + n);
  sort(str2, str2 + n);
  int indi[] = {0, (n + 1) / 2, 0};
  int indj[] = {(n + 1) / 2 - 1, n - 1, n - 1};
  for (int i = 0; i < n; i++) {
    if (i % 2 == 0) {
      if (str1[indi[0]] >= str2[indj[1]]) {
        str3[indj[2]--] = str1[indj[0]--];
      } else {
        str3[indi[2]++] = str1[indi[0]++];
      }
    } else {
      if (str2[indj[1]] <= str1[indi[0]]) {
        str3[indj[2]--] = str2[indi[1]++];
      } else {
        str3[indi[2]++] = str2[indj[1]--];
      }
    }
  }
  printf("%s\n", str3);
}
