from sortedcontainers import SortedList
n, k, x = map(int, input().split())
a = list(map(int, input().split()))
ans = -10**10
b = SortedList([])
for i in range(n):
    b.add(a[i])
    ans = max(ans, sum(b[-k:]) - (i + 1) * x)
print(ans)