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;
typedef pair<int,int> P;
int n;
int t[55];
int m;
int j;
vector<P> ans;
int main() {
  cin >> n;

  bool flag = false;
  for(int i = 0; i < n; i++) {
    cin >> t[i];

    if(m < abs(t[i])) {
      m = abs(t[i]);
      j = i;
      if(t[i] > 0) flag = true;
      else flag = false;
    }
  }


  for(int i = 0; i < n; i++) {
    if(flag) t[i] += m;
    else t[i] -= m;
    ans.push_back(P(j,i));
  }
  
  

  if(flag) {
    for(int i = 1; i < n; i++) {
      ans.push_back(P(i-1,i));
    }
  }
  else {
    for(int i = n-1; i > 0; i--) {
      ans.push_back(P(i,i-1));
    }
  }

  cout << ans.size() << endl;

  for(int i = 0; i < ans.size(); i++) {
    cout << ans[i].first + 1 <<" " << ans[i].second + 1 << endl;
  }
}