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 n;
long long arr[100005];
vector<pair<int,int> > v;

int main()
{
	cin >> n;
	int mn=0,mx=0;
	for(int i=0;i<n;i++)
	{
		cin >> arr[i];
		if(arr[i]<arr[mn]) mn=i;
		if(arr[i]>arr[mx]) mx=i;
	}
	if(mn==mx)
	{
		cout << 0 << endl;
		return 0;
	}
	int cur=(abs(arr[mn])>abs(arr[mx])?mn:mx);
	cur++; // wut?
	cout << (n-1)*2 << endl;
	for(int i=1;i<=n;i++)
	{
		if(i!=cur)
			cout << cur << " " << i << endl;
	}
	if(arr[cur-1]>0) // wut?
		for(int i=1;i<n;i++)
		{
				cout << i << " " << i+1 << endl;
		}
	else
		for(int i=n;i>1;i--)
			cout << i << " " << i-1 << endl;
}