import heapq

n, k, x = map(int, input().split())
a = list(map(int, input().split()))
score = 0
h = []
ans = -(1<<60)
for i, ai in enumerate(a):
    score += ai
    heapq.heappush(h, ai)

    if len(h) > k:
        m = heapq.heappop(h)
        score -= m

    res = score - x * (i + 1)
    ans = max(ans, res)

print(ans)