#include <bits/stdc++.h>
const int maxn = 3e5 + 10;
using namespace std;
char s1[300010], s2[300010], ans[300010];
bool cmp1(const char &a, const char &b) { return a < b; }
bool cmp2(const char &a, const char &b) { return a > b; }
int main() {
  cin >> s1 >> s2;
  int len = strlen(s1);
  sort(s1, s1 + len, cmp1);
  sort(s2, s2 + len, cmp2);
  int i = 0;
  char *pl[2] = {s1, s2};
  while ((i < len) && (*pl[0] < *pl[1])) {
    ans[i] = *(pl[i & 1]++);
    i++;
  }
  int j = len - 1;
  char *pr[2] = {s1 + (len + 1) / 2 - 1, s2 + (len) / 2 - 1};
  while (i < len) {
    ans[j] = *(pr[i & 1]--);
    i++;
    j--;
  }
  ans[len] = '\0';
  cout << ans;
}
