import sys
# input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################

from heapq import *
n, k, x = na()
a = na()
hq = []
s = 0
ans = -10 ** 18
for i in range(n):
    heappush(hq, a[i])
    s += a[i]
    if i >= k:
        s -= heappop(hq)
    # print(i, s)
    ans = max(ans, s - x * (i + 1))

print(ans)