#include <bits/stdc++.h>
using namespace std;
const int maxn = 3e5 + 10;
char s1[maxn], s2[maxn], ans[maxn];
int len;
bool cmp1(const char &a, const char &b) { return a < b; }
bool cmp2(const char &a, const char &b) { return a > b; }
int main() {
  ios::sync_with_stdio(false);
  cin >> s1 >> s2;
  len = strlen(s1);
  sort(s1, s1 + len, cmp1);
  sort(s2, s2 + len, cmp2);
  int i = 0;
  char *pl[2] = {s1, s2};
  for (; (i < len) && (*pl[0] < *pl[1]); ++i) {
    ans[i] = *(pl[i & 1]++);
  }
  int j = len - 1;
  char *pr[2] = {s1 + (len + 1) / 2 - 1, s2 + (len) / 2 - 1};
  for (; i < len; ++i, --j) {
    ans[j] = *(pr[i & 1]--);
  }
  ans[len] = '\0';
  cout << ans;
  return 0;
}
