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;
template <typename T>
inline T abs(T t) {
  return t < 0 ? -t : t;
}
const long long modn = 1000000007;
inline long long mod(long long x) { return x % modn; }
const int MAXN = 312345;
int n, m, k;
char s[2][MAXN];
char res[MAXN];
bool cmp(char a, char b) { return a > b; }
int main() {
  scanf(" %s %s", s[0], s[1]);
  int t[2];
  t[0] = strlen(s[0]);
  t[1] = strlen(s[1]);
  sort(s[0], s[0] + t[0]);
  sort(s[1], s[1] + t[1], cmp);
  int i[2], f[2];
  f[0] = (t[0]) / 2;
  f[1] = (t[1] - 1) / 2;
  i[0] = i[1] = 0;
  int ini = 0, fim = t[0] - 1;
  int id = 0;
  int cnt = 0;
  while (ini <= fim) {
    int ot = id ^ 1;
    if (!id) {
      if (s[ot][i[ot]] < s[id][i[id]])
        res[fim--] = s[id][f[id]--];
      else
        res[ini++] = s[id][i[id]++];
    } else {
      if (s[ot][i[ot]] > s[id][i[id]])
        res[fim--] = s[id][f[id]--];
      else
        res[ini++] = s[id][i[id]++];
    }
    id ^= 1;
    cnt++;
  }
  for (int a = 0; a < t[0]; a++) {
    printf("%c", res[a]);
  }
  printf("\n");
}
