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 = list(map(int,input().split()))

lis = []


mi = float("inf")
ma = float("-inf")
mi_ind = 0
ma_ind = 0

for i in range(N):

    if mi > a[i]:
        mi = a[i]
        mi_ind = i
    if ma < a[i]:
        ma = a[i]
        ma_ind = i
        
flag = None
if mi < 0 and 0 < ma:

    if abs(mi) <= abs(ma):

        flag = 0

        for i in range(N):

            if a[i] < 0:
                lis.append([ma_ind + 1,i+1])

    else:

        flag = 1

        for i in range(N):

            if a[i] > 0:
                lis.append([mi_ind + 1,i+1])

if mi >= 0 or flag == 0:

    for i in range(N-1):

        lis.append([i+1,i+2])

else:

    for i in range(N-1):

        lis.append([N-i,N-1-i])


print (len(lis))

for i in lis:

    print (i[0],i[1])