import heapq

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

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

    ans = max(ans, max_k_sum - X * (i+1))
    
print(ans)