import heapq

N, K, X = map(int, input().split())
A = list(map(int, input().split()))
q = []
s = 0

ret = []

for i in range(N):
	heapq.heappush(q, A[i])
	s += A[i]
	
	if i >= K:
		v = heapq.heappop(q)
		s -= v
	
	val = s - X * (i+1)
	ret.append(val)
	

print(max(ret))