Problem: Snuke has an integer sequence, a, of length N. The i-th element of a (1-indexed) is a_{i}.

He can perform the following operation any number of times:

* Operation: Choose integers x and y between 1 and N (inclusive), and add a_x to a_y.



He would like to perform this operation between 0 and 2N times (inclusive) so that a satisfies the condition below. Show one such sequence of operations. It can be proved that such a sequence of operations always exists under the constraints in this problem.

* Condition: a_1 \leq a_2 \leq ... \leq a_{N}

Constraints

* 2 \leq N \leq 50
* -10^{6} \leq a_i \leq 10^{6}
* All input values are integers.

Input

Input is given from Standard Input in the following format:


N
a_1 a_2 ... a_{N}


Output

Let m be the number of operations in your solution. In the first line, print m. In the i-th of the subsequent m lines, print the numbers x and y chosen in the i-th operation, with a space in between. The output will be considered correct if m is between 0 and 2N (inclusive) and a satisfies the condition after the m operations.

Examples

Input

3
-2 5 -1


Output

2
2 3
3 3


Input

2
-1 -3


Output

1
2 1


Input

5
0 0 0 0 0


Output

0

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
using namespace std;
int INF = 100000000;
int main(){
  int N;
  cin >> N;
  vector<long long> a(N);
  for (int i = 0; i < N; i++){
    cin >> a[i];
  }
  int mxpos = 0;
  int mnpos = 0;
  for (int i = 0; i < N; i++){
    if (a[i] > a[mxpos]){
      mxpos = i;
    }
    if (a[i] < a[mnpos]){
      mnpos = i;
    }
  }
  if (a[mxpos] + a[mnpos] > 0){
    cout << N * 2 - 1 << endl;
    for (int i = 0; i < N; i++){
      cout << mxpos + 1 << ' ' << i + 1 << endl;
    }
    for (int i = 0; i < N - 1; i++){
      cout << i + 1 << ' ' << i + 2 << endl;
    }
  } else {
    cout << N * 2 - 1 << endl;
    for (int i = 0; i < N; i++){
      cout << mnpos + 1 << ' ' << i + 1 << endl;
    }
    for (int i = N - 2; i >= 0; i--){
      cout << i + 2 << ' ' << i + 1 << endl;
    }
  }
}