You can calculate the answer using the following algorithm.

1. Sort \(A\) in ascending order.
2. For each \(B_j\), do the following:
   • 2-1. Find the maximum \(A_i\) that is less than or equal to \(B_j + D\) using binary search. (If such an element does not exist, skip step 2-2.)
   • 2-2. If \(A_i \geq B_j - D\), consider \(A_i + B_j\) as a candidate for the answer.
3. Print the maximum among the answer candidates.

The time complexity of this solution is \(O(N \log N + M \log N)\). Note that it does not necessarily fall behind the official editorial solution, since there is no need to sort \(B\).

Sample Implementation (Python)

import bisect
N, M, D = map(int, input().split())
A = sorted(map(int, input().split()))
B = map(int, input().split())
ans = -1
for b in B:
    i = bisect.bisect_right(A, b + D) - 1
    if i >= 0 and A[i] >= b - D:
        ans = max(ans, A[i] + b)
print(ans)