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 PYTHON):

Solution:

def f(n,ais):
	ma,mi = max(ais), min(ais)
	res = []
	if ma + mi > 0:
		j = [j for j in range(len(ais)) if ais[j] == ma][0]
		for i in range(len(ais)):
			if ais[i] != ma:
				ais[i] += ais[j]
				res.append([j+1,i+1])

		for i in range(1,len(ais)):
			if ais[i-1] > ais[i]:
				ais[i] += ais[i-1]
				res.append([i-1+1, i+1])
	else:
		j = [j for j in range(len(ais)) if ais[j] == mi][0]
		for i in range(len(ais)):
			if ais[i] != mi:
				ais[i] += ais[j]
				res.append([j+1, i+1])
		for i in range(len(ais)-1, 0, -1):
			if not(ais[i - 1] <= ais[i ]):
				ais[i-1] += ais[i]
				res.append([i+1, i-1+1])
	print len(res)
	for u,v in res:
		print u,v
f(int(raw_input()),map(int, raw_input().split()))