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;
const int maxN = 2e3;
int n, arr[maxN];
map<int, vector<pair<int, int> > > seg;
int main() {
  ios_base::sync_with_stdio(0), cin.tie(0), cin.tie(0), cout.tie(0),
      cout.precision(15);
  cin >> n;
  for (int i = int(0); i < int(n); i++) cin >> arr[i];
  for (int i = int(0); i < int(n); i++) {
    int sum = 0;
    for (int j = int(i); j >= int(0); j--) {
      sum += arr[j];
      seg[sum].push_back({j + 1, i + 1});
    }
  }
  vector<pair<int, int> > ans;
  for (auto it : seg) {
    vector<pair<int, int> > curr = it.second;
    vector<pair<int, int> > tt;
    int r = -1;
    for (auto i : curr) {
      if (i.first > r) {
        tt.push_back(i);
        r = i.second;
      }
    }
    if ((int)tt.size() > (int)ans.size()) ans = tt;
  }
  cout << (int)ans.size() << '\n';
  for (auto it : ans) {
    cout << it.first << " " << it.second << '\n';
  }
  return 0;
}