from heapq import heappush, heappop
n, k, x = map(int, input().split())
ans = -10 ** 18
cost = sm = 0
q = []
for a in map(int, input().split()):
    cost += x
    heappush(q, a)
    sm += a
    if len(q) == k + 1:
        sm -= heappop(q)
    ans = max(ans, sm - cost)
print(ans)