from heapq import heappush, heappop

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

SUM = 0
que = []
ans = -(1<<60)
for i, a in enumerate(A):
    SUM += a
    heappush(que, a)
    while K < len(que):
        SUM -= heappop(que)
    ans = max(ans, SUM-X*(i+1))

print(ans)