#include <bits/stdc++.h>
using namespace std;
const int N = 300005;
char a[N], b[N], s[N];
bool cmp(char x, char y) { return x > y; }
int main() {
  scanf("%s%s", a, b);
  int n = strlen(a);
  sort(a, a + n);
  sort(b, b + n, cmp);
  int la = (n - 1) / 2;
  int lb = (n - 2) / 2;
  int pa = 0, pb = 0, p = n + 1;
  for (int i = 1; i <= n; ++i) {
    if (a[pa] >= b[pb]) {
      p = i;
      break;
    }
    if (i & 1)
      s[i] = a[pa++];
    else
      s[i] = b[pb++];
  }
  int q = n;
  pa = la, pb = lb;
  for (int i = p; i <= n; ++i) {
    if (i & 1)
      s[q--] = a[pa--];
    else
      s[q--] = b[pb--];
  }
  for (int i = 1; i <= n; ++i) printf("%c", s[i]);
  puts("");
  return 0;
}
