Problem:
Score : 500 points

Problem Statement

We have a sequence of N integers: A_1, A_2, \cdots, A_N.

You can perform the following operation between 0 and K times (inclusive):

Choose two integers i and j such that i \neq j, each between 1 and N (inclusive). Add 1 to A_i and -1 to A_j, possibly producing a negative element.

Compute the maximum possible positive integer that divides every element of A after the operations. Here a positive integer x divides an integer y if and only if there exists an integer z such that y = xz.

Constraints

2 \leq N \leq 500

1 \leq A_i \leq 10^6

0 \leq K \leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N K
A_1 A_2 \cdots A_{N-1} A_{N}

Output

Print the maximum possible positive integer that divides every element of A after the operations.

Sample Input 1

2 3
8 20

Sample Output 1

7

7 will divide every element of A if, for example, we perform the following operation:

Choose i = 2, j = 1. A becomes (7, 21).

We cannot reach the situation where 8 or greater integer divides every element of A.

Sample Input 2

2 10
3 5

Sample Output 2

8

Consider performing the following five operations:

Choose i = 2, j = 1. A becomes (2, 6).

Choose i = 2, j = 1. A becomes (1, 7).

Choose i = 2, j = 1. A becomes (0, 8).

Choose i = 2, j = 1. A becomes (-1, 9).

Choose i = 1, j = 2. A becomes (0, 8).

Then, 0 = 8 \times 0 and 8 = 8 \times 1, so 8 divides every element of A. We cannot reach the situation where 9 or greater integer divides every element of A.

Sample Input 3

4 5
10 1 2 22

Sample Output 3

7

Sample Input 4

8 7
1 7 5 6 8 2 6 5

Sample Output 4

5

Solution in PyPy3 (7.3.0) (judge verdict: Accepted)

import sys, math
from collections import defaultdict
input = sys.stdin.readline
rs = lambda: input().strip()
ri = lambda: int(input())
rl = lambda: list(map(int, input().split()))
mod = 1000000007
sys.setrecursionlimit(1000000)

N, K = rl()
A = rl()

s = sum(A)
m = math.ceil(math.sqrt(s))

divs = []
divs2 = []
i = 1
while i <= m:
	if s % i == 0:
		divs.append(i)
		divs2.append(s//i)
	i += 1
divs.reverse()
divs2 += divs

ans = 1
for n in divs2:
	B = [a % n for a in A]
	s = sum(B)
	if s % n != 0: continue
	B.sort()
	B = [b for b in B if b != 0]
	if len(B) == 0:
		ans = max(ans, n)
		break
	bsum = [0]*len(B)
	rbsum = [0]*len(B)
	bs = 0
	for i, b in enumerate(B):
		bs += b
		bsum[i] = bs
	bs = 0
	for i in range(len(B)-1, -1, -1):
		bs += n - B[i]
		rbsum[i] = bs
	need = float('inf')
	for i in range(len(B)-1):
		if bsum[i] == rbsum[i+1]:
			need = bsum[i]
			break
	if need <= K:
		ans = max(ans, n)
		break
print(ans)