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:
def getN():
    return int(input())

def getMN():
    a = input().split()
    b = [int(i) for i in a]
    return b[0],b[1]

def getlist():
    a = input().split()
    b = [int(i) for i in a]
    return b

n = getN()
nums = getlist()
ln = len(nums)
maxn, minn = max(nums), min(nums)
already = False

if minn >= 0:
    plus = True

if maxn < 0:
    plus = False

if maxn >= 0 and minn < 0:
    print(ln*2-1)
    already = True
    if abs(maxn) > abs(minn):
        source = nums.index(maxn)
        plus = True
    else:
        source = nums.index(minn)
        plus = False
    for i in range(len(nums)):
        print(source+1, i+1)

if not already:
    print(ln-1)

if plus:
    for i in range(ln-1):
        print(i+1, i+2)
else:
    for i in range(ln-1):
        print(ln-i, ln-i-1)