N,K,X = map(int, input().split())
A_li = list(map(int, input().split()))
# f_li = [0] * N
ans = float("-inf") # 负无穷

import heapq
max_k = [] # 小根堆，用来存A_li中最大的K个元素
for i in range(N):
    if len(max_k) < K:
        heapq.heappush(max_k, A_li[i])
    elif A_li[i] > max_k[0]:
        heapq.heapreplace(max_k, A_li[i])

    # f_li[i] = sum(max_k) - X * (i+1)
    ans = max(ans, sum(max_k) - X * (i+1))
    
# print(f_li)
print(ans)