#!/usr/bin/env python3
(n, k), ds = (list(map(int, input().split())) for _ in "..")
end_times, prev, ans = ds[:k], 0, 0
for t in ds[k:]:
    curr = min(end_times)
    end_times.remove(curr)
    ans = max(ans, curr - prev)
    end_times.append(curr + t)
    prev = curr
while end_times:
    curr = min(end_times)
    end_times.remove(curr)
    ans = max(ans, curr - prev)
    prev = curr
print(ans)