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 CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
int a[2000];
map<int, vector<pair<int, int>>> mp, o;
int main(void) {
  std::ios::sync_with_stdio(false);
  cin.tie(0);
  int n, x;
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) scanf("%d", &x), a[i] = a[i - 1] + x;
  for (int i = 1; i <= n; ++i)
    for (int j = i; j >= 1; --j) mp[a[i] - a[j - 1]].push_back(make_pair(j, i));
  int ans = 0, maxsize = 0;
  for (auto &v : mp) {
    for (int i = 0, j = -1; i < v.second.size(); ++i)
      if (j == -1 || v.second[i].first > v.second[j].second)
        o[v.first].push_back(v.second[i]), j = i;
    if (maxsize < o[v.first].size()) ans = v.first, maxsize = o[v.first].size();
  }
  printf("%d\n", maxsize);
  for (auto v : o[ans]) printf("%d %d\n", v.first, v.second);
  return 0;
}