from heapq import heappop, heappush

N, K, X = map(int, input().split())
A = list(map(int, input().split()))

nk = 0
total = 0
que = []
ret = -1000_000_000_000

for i in range(N):
    nk += 1
    total += A[i]
    heappush(que, A[i])
    if nk > K:
        rmv = heappop(que)
        total -= rmv
        nk -= 1
    now = total - X * (i + 1)
    ret = max(ret, now)
print(ret)