from bisect import bisect_left, bisect_right, insort
N, K, X = map(int, input().split())
A = list(map(int, input().split()))

L = []
total = 0
ans = -1e18
for i in range(N):
    a = A[i]
    if i < K:
        total += a
        insort(L, a)
    else:
        # a はどこにはいるか？
        idx = bisect_right(L, a)
        if i - K + 1 <= idx: # 上位K人にランクインできる
            total -= L[i - K]
            total += a
            insort(L, a)
        else:
            insort(L, a)

    # i+1 個の要素がある
    memo = total - (i + 1)*X

    if memo > ans:
        ans = memo

print(ans)