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 = [int(i) for i in input().split()]
a_max = max(a)
a_min = min(a)

abs_max = a_min if abs(a_min) > abs(a_max) else a_max
abs_max_index = a.index(abs_max)


print(2*n-1)

total = 0

for i in range(n):

    print(abs_max_index+1, i+1)
    a[i] += abs_max

my_range, next_index_diff = (
    list(range(n-1)), 1) if abs_max > 0 else (list(range(n-1, 0, -1)), -1)


while my_range:

    index = my_range.pop(0)

    print(index+1, index+1+next_index_diff)
    a[index+next_index_diff] += a[index]