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

import heapq
hq = []
sm = 0
ans = -10**18
for i,a in enumerate(A,1):
    heapq.heappush(hq, a)
    sm += a
    if len(hq) > K:
        sm -= heapq.heappop(hq)
    ans = max(ans, sm - i*X)
print(ans)