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;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
inline long long int rand(long long int x, long long int y) {
  ++y;
  return (rng() % (y - x)) + x;
}
long long int n, k, co = 1, A[1506];
map<long long int, int> mp;
vector<pair<long long int, long long int> > v[1500 * 1500 + 6], anss;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cin >> n;
  for (long long int i = 0; i < n; i++) cin >> A[i];
  for (long long int i = 0; i < n; i++) {
    long long int sum = 0;
    for (long long int j = i; j < n; j++) {
      sum += A[j];
      if (mp[sum] == 0) mp[sum] = co++;
      v[mp[sum]].push_back(pair<long long int, long long int>(i, j));
    }
  }
  for (long long int i = 1; i < co; i++) {
    long long int ans = 0, l = -1;
    vector<pair<long long int, long long int> > pa;
    sort((v[i]).begin(), (v[i]).end(),
         [](pair<long long int, long long int> x,
            pair<long long int, long long int> y) {
           return x.second < y.second;
         });
    for (auto j : v[i]) {
      if (j.first > l) ans++, l = j.second, pa.push_back(j);
    }
    if (k < ans) anss = pa;
    k = max(k, ans);
  }
  cout << k << '\n';
  for (auto j : anss) cout << j.first + 1 << ' ' << j.second + 1 << '\n';
  cout << '\n';
}