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:
from sys import stdin
from collections import defaultdict
def ip(): return [int(i) for i in stdin.readline().split()]
def sp(): return [str(i) for i in stdin.readline().split()]
def pp(A): 
    for i in A: print(i)



def solve():
    n = int(input())
    A = ip()
    d = defaultdict(list)
    for i in range(n):
        rs = 0
        for j in range(i, n):
            rs += A[j]
            d[rs].append((i,j))
    ans = float('-inf')
    B = []
    for k in d:
        cnt = 0
        r = -1
        blocks = []
        d[k].sort(key=lambda x: x[1])
        for i in d[k]:
            if i[0] > r:
                cnt += 1
                r = i[1]
                blocks.append((i[0], i[1]))
        # print(f'{k=} | {cnt=} | {blocks=}')
        if cnt >= ans:
            ans = cnt
            B = blocks.copy()
    print(ans)
    for i,j in B:
        print(i+1, j+1)

solve()