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:

// D - Non-decreasing

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int INF = 2147483647;
// const ll INF = 9223372036854775807;
// const ll MOD = 1e9 + 7;

int a[50];

int main() {
	int N;
	cin >> N;

	int max_i = 0;
	for (int i=0; i<N; i++) {
		cin >> a[i];
		if (abs(a[i]) > abs(a[max_i])) max_i = i;
	}

	cout << 2 * N - 1 << endl;

	for (int i=0; i<N; i++) {
		a[i] += a[max_i];
		cout << max_i+1 << " " << i+1 << endl;
	}


	if (a[max_i] >= 0) {
		for (int i=0; i<N-1; i++) {
			a[i+1] += a[i];
			cout << i+1 << " " << i+2 << endl;
		}
	} else {
		for (int i=N-1; i>0; i--) {
			a[i-1] += a[i];
			cout << i+1 << " " << i << endl;
		}
	}

	return 0;
}