from heapq import heappush, heappop
N, K, X = map(int, input().split())
A = list(map(int, input().split()))

L = []
total = 0
ans = -1e18
for i in range(N):
    a = A[i]
    heappush(L, a)
    total += a
    if i >= K:
        rm = heappop(L)
        total -= rm
    memo = total - (i + 1)*X
    if memo > ans:
        ans = memo

print(ans)