import sys
import math
#from collections import deque, defaultdict, Counter
#import heapq
#import bisect
#import itertools
#import functools

# 外部ライブラリ（AtCoder環境で利用可能）
#from sortedcontainers import SortedList, SortedSet, SortedDict
#from atcoder.dsu import DSU
#from atcoder.segtree import SegTree
#from atcoder.lazysegtree import LazySegTree
#from atcoder.fenwicktree import FenwickTree

# 入力高速化
#input = sys.stdin.readline
# 再帰回数上限

# よくあるmod
#MOD = 1000000007
MOD = 998244353

def solve():
    # 解答ここから
    N, K, X = map(int, input().split(' '))
    A = list(map(int, input().split(' ')))
    cnt = 0
    cur = 0 # sum
    ans = -10000000000000
    import heapq
    hq = []
    for i in range(N):
        cur += A[i]
        heapq.heappush(hq, A[i])
        cnt += 1
        if cnt == K+1:
            cur -= heapq.heappop(hq)
            cnt -= 1
        ans = max(ans, cur - (i+1) * X)
    print(ans)
        
if __name__ == '__main__':
    T = 1
    for _ in range(T):
        solve()