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 MAX_N = 300000;
char s[MAX_N + 4], t[MAX_N + 4], w[MAX_N + 4];
int main() {
  scanf("%s%s", s, t);
  int n = strlen(s);
  sort(s, s + n);
  sort(t, t + n);
  int sh = 0, st = (n + 1) / 2, th = st, tt = n;
  for (int i = 0, j = n, k = 0; i < j; k ^= 1) {
    if (!k) {
      if (th < tt && s[sh] >= t[tt - 1])
        w[--j] = s[--st];
      else
        w[i++] = s[sh++];
    } else {
      if (sh < st && t[tt - 1] <= s[sh])
        w[--j] = t[th++];
      else
        w[i++] = t[--tt];
    }
  }
  puts(w);
  return 0;
}
