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>
#include <vector>
using namespace std;
const int INF = 1001001001;

int main() {
	int n;
	cin >> n;
	vector<pair<int, int>> ans;
	int mina = INF, maxa = -INF, minidx, maxidx;
	for (int i = 0; i < n; i++) {
		int a;
		cin >> a;
		if (a < mina) {
			mina = a;
			minidx = i;
		}
		if (a > maxa) {
			maxa = a;
			maxidx = i;
		}
	}
	if (abs(maxa) > abs(mina)) {
		for (int i = 0; i < n; i++) {
			if (i == maxidx) continue;
			ans.emplace_back(maxidx, i);
		}
		for (int i = 0; i < n-1; i++) {
			ans.emplace_back(i, i+1);
		}
	} else {
		for (int i = 0; i < n; i++) {
			if (i == minidx) continue;
			ans.emplace_back(minidx, i);
		}
		for (int i = n-1; i > 0; i--) {
			ans.emplace_back(i, i-1);
		}
	}
	cout << ans.size() << endl;
	for (auto e : ans) {
		cout << e.first+1 << ' ' << e.second+1 << endl;
	}
	return 0;
}