n, k, x = map(lambda s_: int(s_), input().split())
a = tuple(map(lambda s_: int(s_), input().split()))

q = []
tot = 0
from heapq import heappush, heappop

ans = -(10**20)
for i, ai in enumerate(a, 1):
    heappush(q, ai)
    tot += ai
    while len(q) > k:
        e = heappop(q)
        tot -= e
    ans = max(ans, tot - i * x)
print(ans)