#include <bits/stdc++.h>
using namespace std;
int cmp(char a, char b) { return a > b; }
int main() {
  char s[300050];
  char str[300050];
  char ans[300050];
  scanf("%s%s", s, str);
  int len = strlen(s);
  sort(s, s + len);
  sort(str, str + len, cmp);
  if (len == 1) {
    printf("%s\n", s);
    return 0;
  }
  int l, r, L, R;
  l = L = 0;
  r = (len + 1) / 2 - 1;
  if (len & 1) {
    R = len / 2 - 1;
  } else
    R = r;
  int sum = 0;
  int i = 0;
  int j = len - 1;
  while (i <= j) {
    if ((sum & 1) == 0) {
      if (s[l] < str[L]) {
        ans[i++] = s[l++];
      } else {
        ans[j--] = s[r--];
      }
      sum++;
    } else {
      if (s[l] >= str[L]) {
        ans[j--] = str[R--];
      } else {
        ans[i++] = str[L++];
      }
      sum++;
    }
  }
  ans[len] = '\0';
  printf("%s\n", ans);
  return 0;
}
