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:
n = int(raw_input())
a = map(int,raw_input().split(" "))

ans = []
aa = sorted(a)

if aa[0] < 0 and aa[n-1] > 0:
  bt = aa[0]
  up = aa[n-1]
  if abs(bt) > abs(up):
    r = a.index(bt)
    for x in range(n):
      if x != r:
        a[x] += bt
        ans.append([r+1,x+1])
  else:
    r = a.index(up)
    for x in range(n):
      if x != r:
        a[x] += up
        ans.append([r+1,x+1])

aa = sorted(a)

if aa[0] == aa[n-1]:
  print 0
  exit()

if aa[0] >= 0: # all plus!
  for x in range(n-1):
    a[x+1] += a[x]
    ans.append([x+1,x+2])
elif aa[n-1] <= 0: # all minus!
  for x in range(n-2,-1,-1):
    a[x] += a[x+1]
    ans.append([x+2,x+1])

print len(ans)
for q in ans:
  print "%d %d" % (q[0],q[1])