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()))

Ans = []
maxA,minA,maxAi,minAi = A[0],A[0],0,0
for i in range(1,N):
    if A[i] > maxA:
        maxA = A[i]
        maxAi = i
    if A[i] < minA:
        minA = A[i]
        minAi = i

if abs(maxA) >= abs(minA):
    for i in range(N):
        if i != maxAi:
            Ans.append((maxAi,i))
    for i in range(N-1):
        Ans.append((i,i+1))
else:
    for i in range(N):
        if i != minAi:
            Ans.append((minAi,i))
    for i in range(N-1):
        Ans.append((N-1-i,N-1-i-1))

print(len(Ans))
for (x,y) in Ans:
    print(x+1,y+1)