#include <bits/stdc++.h>
using namespace std;
const int N = 3e5 + 5;
char a[N], b[N], ans[N];
int main() {
  scanf("%s", a);
  scanf("%s", b);
  int n = strlen(a);
  sort(a, a + n);
  sort(b, b + n);
  reverse(b, b + n);
  int la = 0, lb = (n + 1) >> 1;
  int ra = 0, rb = n >> 1;
  int l = 0, r = n;
  for (int i = 0; i < n; i++) {
    if (i & 1) {
      if (a[la] < b[ra])
        ans[l++] = b[ra++];
      else
        ans[--r] = b[--rb];
    } else {
      if (a[la] < b[ra])
        ans[l++] = a[la++];
      else
        ans[--r] = a[--lb];
    }
  }
  ans[n] = 0;
  puts(ans);
  return 0;
}
