bcdef
abbbc
 z
y
 reddit
abcdef
 abc
aaa
 y
z
 cbxz
aaaa

bccdb
 z
 dfdeed
 aab
 y
 abac

#include <bits/stdc++.h>
char a[300002], b[300002], c[300002];
int main() {
  scanf("%s%s", a, b);
  int n = strlen(a), ca = 0, cb = 0;
  int maxa, maxb;
  std::sort(a, a + n);
  std::sort(b, b + n);
  std::reverse(b, b + n);
  if (n % 2 == 1)
    maxa = n / 2, maxb = n / 2 - 1;
  else
    maxa = maxb = n / 2 - 1;
  int i;
  for (i = 0; i < n; i++)
    if (~i & 1) {
      if (ca <= maxa && cb <= maxb && a[ca] > b[cb]) break;
      c[i] = a[ca++];
    } else {
      if (ca <= maxa && cb <= maxb && b[cb] < a[ca]) break;
      c[i] = b[cb++];
    }
  if (~i & 1) {
    int t = i;
    bool flag = 1;
    for (i = n - 1; i >= t; --i)
      if (flag) {
        flag = !flag;
        c[i] = a[maxa--];
      } else {
        flag = !flag;
        c[i] = b[maxb--];
      }
  } else {
    int t = i;
    bool flag = 0;
    for (i = n - 1; i >= t; --i)
      if (flag) {
        flag = !flag;
        c[i] = a[maxa--];
      } else {
        flag = !flag;
        c[i] = b[maxb--];
      }
  }
  c[n] = 0;
  printf("%s", c);
  return 0;
}
