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

line = sys.stdin.readline().strip()
N = int(line)
line = sys.stdin.readline().strip()
A = [int(x) for x in line.split()]

#N = 4
#A = [-2, -6, -1, -4]
#A = [0, 1, 0, 0]

#print(N)
#print(A)
vs = sorted([(x, i) for i, x in enumerate(A)])
k = vs[0] if abs(vs[0][0]) > abs(vs[-1][0]) else vs[-1]
#print(k)

tejun = []

def mv(i, j):
    tejun.append((i, j))
    A[j] += A[i]
    #print("*", i, j, A)

if k[0] > 0:
  mv(k[1], 0)
  mv(k[1], 0)
  for i in range(1, N):
      mv(i - 1, i)
      mv(i - 1, i)
elif k[0] < 0:
  mv(k[1], N - 1)
  mv(k[1], N - 1)
  for i in range(N, 1, -1):
      mv(i - 1, i - 2)
      mv(i - 1, i - 2)
else:
    pass

print(len(tejun))
for t in tejun:
    print(t[0] + 1, t[1] + 1)