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 <iostream>

using namespace std;

int N;
long long int a[55];

int main(void) {

	cin >> N;

	long long int tmp;

	for (int i = 1; i <= N; i++) {
		cin >> tmp; a[i] = tmp;
	}

	int sig = 0;
	int max_ab = 0;
	int I;
	for (int i = 1; i <= N; i++) {
		if (abs(a[i]) >= max_ab) { max_ab = abs(a[i]); I = i; if (a[i] >= 0) { sig = 1; }
		else { sig = -1; }
		}
	}


	cout << 2 * N-1 << endl;
	if (sig == 1) {
		for (int i = 1; i <= N; i++) {
			cout << I << " " << i << endl;
		}
		for (int i = 1; i <= N-1; i++) {
			cout << i << " " << i + 1 << endl;
		}
	}
	else {
		for (int i = 1; i <= N; i++) {
			cout << I << " " << i << endl;
		}
		for (int i = N; i >= 2; i--) {
			cout << i << " " << i - 1 << endl;
		}

	}

	//system("pause");
	return 0;
}