Problem:
Score : 400 points

Problem Statement

Takahashi will play a game using a piece on an array of squares numbered 1, 2, \cdots, N. Square i has an integer C_i written on it. Also, he is given a permutation of 1, 2, \cdots, N: P_1, P_2, \cdots, P_N.

Now, he will choose one square and place the piece on that square. Then, he will make the following move some number of times between 1 and K (inclusive):

In one move, if the piece is now on Square i (1 \leq i \leq N), move it to Square P_i. Here, his score increases by C_{P_i}.

Help him by finding the maximum possible score at the end of the game. (The score is 0 at the beginning of the game.)

Constraints

2 \leq N \leq 5000

1 \leq K \leq 10^9

1 \leq P_i \leq N

P_i \neq i

P_1, P_2, \cdots, P_N are all different.

-10^9 \leq C_i \leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N K
P_1 P_2 \cdots P_N
C_1 C_2 \cdots C_N

Output

Print the maximum possible score at the end of the game.

Sample Input 1

5 2
2 4 5 1 3
3 4 -10 -8 8

Sample Output 1

8

When we start at some square of our choice and make at most two moves, we have the following options:

If we start at Square 1, making one move sends the piece to Square 2, after which the score is 4. Making another move sends the piece to Square 4, after which the score is 4 + (-8) = -4.

If we start at Square 2, making one move sends the piece to Square 4, after which the score is -8. Making another move sends the piece to Square 1, after which the score is -8 + 3 = -5.

If we start at Square 3, making one move sends the piece to Square 5, after which the score is 8. Making another move sends the piece to Square 3, after which the score is 8 + (-10) = -2.

If we start at Square 4, making one move sends the piece to Square 1, after which the score is 3. Making another move sends the piece to Square 2, after which the score is 3 + 4 = 7.

If we start at Square 5, making one move sends the piece to Square 3, after which the score is -10. Making another move sends the piece to Square 5, after which the score is -10 + 8 = -2.

The maximum score achieved is 8.

Sample Input 2

2 3
2 1
10 -7

Sample Output 2

13

Sample Input 3

3 3
3 1 2
-1000 -2000 -3000

Sample Output 3

-1000

We have to make at least one move.

Sample Input 4

10 58
9 1 6 7 8 4 3 2 10 5
695279662 988782657 -119067776 382975538 -151885171 -177220596 -169777795 37619092 389386780 980092719

Sample Output 4

29507023469

The absolute value of the answer may be enormous.

Solution in Python (3.8.2) (judge verdict: Time Limit Exceeded)

import sys
import numpy as np

# 公式解説を見てからやった
# 複数サイクルでき、1-K回移動可能
# N < 5000?多分、O(N * 2N)くらいで行けそうに見えるが。。。

def main(N,K,P,C):


	# 一度計算したサイクル情報を一応キャッシュしておく。。。
	# あんまり意味なさそう
	cycleIDs = np.full( N, -1, dtype=np.int64 )
	cycleInfs = []


	# print(P)

	ans = -1e19
	cycleID = 0

	for n in range(N):

		v = n
		currentCycleItemCnt = 0
		currentCycleTotal = 0

		if cycleIDs[v] != -1:
			currentCycleItemCnt, currentCycleTotal = cycleInfs[ cycleIDs[v] ]
			# print(currentCycleItemCnt, currentCycleTotal)
		else:
			while True:
				# 全頂点について、属するサイクルを計算する
				currentCycleItemCnt += 1
				currentCycleTotal += C[v]

				v = P[v]
				if v == n:
					# サイクル発見
					cycleInfs.append( (currentCycleItemCnt, currentCycleTotal) )
					cycleID += 1
					break

				# 一応、一度サイクルを計算した頂点については、
				# その頂点の属するサイクルの情報をメモっておく。。。
				cycleIDs[v] = cycleID

		procCnt = 0
		currentCycleSumTmp = 0

		while True:

			# 頂点vにコマが置かれた時の最高スコアを計算し、
			# これまでの最高スコアを上回ったら、これまでの最高スコアを更新する
			procCnt += 1
			currentCycleSumTmp += C[v]
			if K < procCnt:
				break

			cycleLoopCnt = 0
			if procCnt < K and 0 < currentCycleTotal:
				cycleLoopCnt = int(( K - procCnt ) // currentCycleItemCnt)

			# print("v=", v, "currentCycleSumTmp=", currentCycleSumTmp, procCnt)
			tmp = currentCycleSumTmp + cycleLoopCnt * currentCycleTotal
			ans = max( int(ans), int(tmp) )

			v = P[v]
			if v == n:
				# サイクル終了
				break

	print(int(ans))


if __name__ == "__main__":
	N,K = map(int,input().split())
	P = np.array( input().split(), np.int64 )
	P -= 1
	C = np.array( input().split(), np.int64 )

	main(N,K,P,C)
	#print(ans)