#include <bits/stdc++.h>
using namespace std;
inline void fre1() {
  freopen("C:\\Users\\Administrator\\Desktop\\in.txt", "r", stdin);
  freopen("C:\\Users\\Administrator\\Desktop\\out.txt", "w", stdout);
}
inline void fre2() {
  fclose(stdin);
  fclose(stdout);
}
const long long mod = 1e9 + 7;
const int maxn = 3e5 + 20, maxm = 1e3 + 20, INF = 1e9 + 7;
const double PI = acos(-1), eps = 1e-7;
int n, m, h;
char s[maxn];
char t[maxn];
char ans[maxn];
int main() {
  scanf("%s %s", s, t);
  int n = strlen(s);
  int l2 = n / 2;
  int l1 = n - l2;
  sort(s, s + n);
  sort(t, t + n);
  reverse(t, t + n);
  int n1 = 0;
  int n2 = 0;
  int l = 0;
  int r = n - 1;
  for (int i = 0; i < n; ++i) {
    if (i % 2 == 0) {
      if (n2 != l2 && t[n2] <= s[n1]) {
        ans[r] = s[l1 - 1];
        --l1;
        --r;
      } else {
        ans[l] = s[n1];
        ++n1;
        ++l;
      }
    } else {
      if (n1 != l1 && s[n1] >= t[n2]) {
        ans[r] = t[l2 - 1];
        --l2;
        --r;
      } else {
        ans[l] = t[n2];
        ++n2;
        ++l;
      }
    }
  }
  printf("%s\n", ans);
  return 0;
}
