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()))

m = 0
manu = []

for i in range(1,N):
    if abs(a[m]) < abs(a[i]):
        m = i

for i in range(N):
    if a[m]*a[i] < 0:
        a[i] += a[m]
        manu.append([m,i])

if a[m] >= 0:
    for i in range(N-1):
        if a[i] > a[i+1]:
            a[i+1] += a[i]
            manu.append([i,i+1])

else:
    for i in range(N-1):
        if a[N-i-2] > a[N-i-1]:
            a[N-i-2] += a[N-i-1]
            manu.append([N-i-1,N-i-2])
    
print(len(manu))
for i in range(len(manu)):
    manu[i][0] += 1
    manu[i][1] += 1
    print(" ".join(list(map(str,manu[i]))))