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 PYTHON3):

Solution:
n = int(input())
a = list(map(int, input().split()))

b = 0
by = 0
flg = 0
for i,j in enumerate(a):
	if abs(j) > abs(b):
		b = j
		by = i+1
		if j > 0:
			flg = 1
		else:
			flg = 0
ans = []
if flg == 1:
	x = min(a)
	if x < 0:
		for i in range(n):
			if a[i] != b:
				a[i] += b
				ans.append([by,i+1])
	for i in range(1,n):
		a[i] += a[i-1]
		ans.append([i,i+1])
else:
	x = max(a)
	if x > 0:
		for i in range(n-1,-1,-1):
			if a[i] != b:
				a[i] += b
				ans.append([by,i+1])
	for i in range(n-2,-1,-1):
		a[i] += a[i+1]
		ans.append([i+2,i+1])
print (len(ans))
for i in ans:
	print (*i)