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:
import sys
read=sys.stdin.read

n,*a=map(int,read().split())
def output(x,y):
  #a[y]+=a[x]
  print('{} {}'.format(x+1,y+1))
mx=max(a)
mxi=a.index(mx)
mn=min(a)
mni=a.index(mn)

print(2*n-1)
if abs(mx)>=abs(mn) and mx>=0:
  for i in range(n):
    if mxi!=i:
      output(mxi,i)
  output(mxi,mxi)
  for i in range(1,n):
    output(i-1,i)
elif abs(mx)<abs(mn) and mn<0:
  for i in range(n):
    if mni!=i:
      output(mni,i)
  output(mni,mni)
  for i in range(n-1,0,-1):
    output(i,i-1)