from sortedcontainers import SortedList
N, K, X = map(int, input().split())
A = list(map(int, input().split()))
sl = SortedList()
s = 0

ret = []

for i in range(N):
	sl.add(A[i])
	s += A[i]
	
	if i >= K:
		v = sl[0]
		sl.discard(v)
		s -= v
	
	val = s - X * (i+1)
	ret.append(val)
	

print(max(ret))