Problem: This problem is given in two editions, which differ exclusively in the constraints on the number n.

You are given an array of integers a[1], a[2], ..., a[n]. A block is a sequence of contiguous (consecutive) elements a[l], a[l+1], ..., a[r] (1 ≤ l ≤ r ≤ n). Thus, a block is defined by a pair of indices (l, r).

Find a set of blocks (l_1, r_1), (l_2, r_2), ..., (l_k, r_k) such that:

  * They do not intersect (i.e. they are disjoint). Formally, for each pair of blocks (l_i, r_i) and (l_j, r_j) where i ≠ j either r_i < l_j or r_j < l_i. 
  * For each block the sum of its elements is the same. Formally, $$$a[l_1]+a[l_1+1]+...+a[r_1]=a[l_2]+a[l_2+1]+...+a[r_2]= ... = a[l_k]+a[l_k+1]+...+a[r_k].$$$ 
  * The number of the blocks in the set is maximum. Formally, there does not exist a set of blocks (l_1', r_1'), (l_2', r_2'), ..., (l_{k'}', r_{k'}') satisfying the above two requirements with k' > k. 

<image> The picture corresponds to the first example. Blue boxes illustrate blocks.

Write a program to find such a set of blocks.

Input

The first line contains integer n (1 ≤ n ≤ 1500) — the length of the given array. The second line contains the sequence of elements a[1], a[2], ..., a[n] (-10^5 ≤ a_i ≤ 10^5).

Output

In the first line print the integer k (1 ≤ k ≤ n). The following k lines should contain blocks, one per line. In each line print a pair of indices l_i, r_i (1 ≤ l_i ≤ r_i ≤ n) — the bounds of the i-th block. You can print blocks in any order. If there are multiple answers, print any of them.

Examples

Input


7
4 1 2 2 1 5 3


Output


3
7 7
2 3
4 5


Input


11
-5 -4 -3 -2 -1 0 1 2 3 4 5


Output


2
3 4
1 1


Input


4
1 1 1 1


Output


4
4 4
1 1
2 2
3 3

Solution (in PYTHON3):

Solution:
def find(v: int, s: int):
    global d, a, n
    left, r = 0, v
    if s == -5:
        print('v', v, d[s][v], d[s][:v])
    while r - left > 1:
        mid = (left + r) // 2
        if s == -5 and v == 6:
            print(d[s][v][0], d[s][mid][1])
        if d[s][v][0] > d[s][mid][1]:
            left = mid
        else:
            r = mid
    return left


n = int(input())
a = list(map(int, input().split()))
d = dict()
for i in range(n):
    s = 0
    for j in range(i, n):
        s += a[j]
        if s in d:
            d[s].append((i + 1, j + 1))
        else:
            d[s] = [(i + 1, j + 1)]
for i in d.keys():
    d[i].sort(key=lambda x: x[1])

# print(d)
ar = []
for el in d.keys():
    cur = []
    r = 0
    for i in d[el]:
        if i[0] > r:
            cur.append(i)
            r = i[1]
    if len(ar) < len(cur):
        ar = cur

print(len(ar))
for i in ar:
    print(*i)