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<cstdio>

int main(){
	int N;
	scanf("%d", &N);
	long int max_absolute_value = 0;
	int max_absolute_value_id = 1; 
	for (int i = 1; i <= N; ++i) {
		long int tmp;
		scanf("%ld", &tmp);
		if(tmp * tmp > max_absolute_value * max_absolute_value) {
			max_absolute_value = tmp;
			max_absolute_value_id = i;
		}
	}
	printf("%d\n", N * 2 - 2);
	for (int i = 1; i <= N; ++i) {
		if(i != max_absolute_value_id)
			printf("%d %d\n", max_absolute_value_id, i);
	}
	if(max_absolute_value >= 0) {
		for(int i = 1; i < N; ++i)
			printf("%d %d\n", i, i+1);
	} else {
		for(int i = N; i > 1; --i)
			printf("%d %d\n", i, i-1);
	}
	return 0;
}