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>
#define INF64 1LL << 60;
#define INF32 1 << 29;

using namespace std;

void execute()
{
	int n;
	int max = -INF32;
	int min = INF32;
	int pos_max = -1, pos_min = -1;
	bool pm;
	int tmp;
	cin >> n;
	for (int i = 0; i < n; i++)
	{
		cin >> tmp;
		if (max < tmp)
		{
			max = tmp;
			pos_max = i;
		}
		if (tmp < min)
		{
			min = tmp;
			pos_min = i;
		}
	}

	pm = abs(min) <= abs(max);

	cout << (n * 2 - 1) << endl;
	for (int i = 0; i < n; i++)
	{
		cout << (pm ? pos_max : pos_min) + 1 << " " << i + 1 << endl;
	}
	for (int i = 0; i < n - 1; i++)
	{
		int j = pm ? i : n - 1 - i;
		cout << j + 1 << " " << j + (pm ? 1 : -1) + 1 << endl;
	}

	return;
}

int main()
{
	std::cout << std::fixed << std::setprecision(15);
	execute();

	int stop;
	cin >> stop;

	return 0;
}