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 main() {
	int N;
	cin >> N;
	vector<int>A(N);
	int nmin = 1e9;
	int nmax = -1e9;
	for (int i = 0; i < N; ++i) {
		cin >> A[i];
		nmin = min(nmin, A[i]);
		nmax = max(nmax, A[i]);
	}
	cout << 2 * N - 1 << endl;
	if (abs(nmin) >= abs(nmax)) {
		int i;
		for (i = 0; i < N; ++i) {
			if (nmin == A[i]) {
				break;
			}
		}
		for (int j = 0; j < N; ++j) {
			cout << i + 1 << " " << j + 1 << endl;
		}
		for (int j = 0; j < N - 1; ++j) {
			cout << N - j << " " << N - j - 1 << endl;
		}
	}
	else {
		int i;
		for (i = 0; i < N; ++i) {
			if (nmax == A[i]) {
				break;
			}
		}
		for (int j = 0; j < N; ++j) {
			cout << i + 1 << " " << j + 1 << endl;
		}
		for (int j = 0; j < N - 1; ++j) {
			cout << j + 1 << " " << j + 2 << endl;
		}
	}

	return 0;
}