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,*a=map(int,open(0).read().split())
ans=[]
if sum(t for t in a if t>0)>sum(-t for t in a if t<0):
    i=0
    while a[i]<0:i+=1
    for j in range(n):
        if a[j]>0and i!=j:
            a[i]+=a[j]
            ans+=[(j+1,i+1)]
    for j in range(n):
        if a[j]<0:
            a[j]+=a[i]
            ans+=[(i+1,j+1)]
    for i in range(1,n):
        ans+=[(i,i+1)]
else:
    i=0
    while a[i]>0:i+=1
    for j in range(n):
        if a[j]<0and i!=j:
            a[i]+=a[j]
            ans+=[(j+1,i+1)]
    for j in range(n):
        if a[j]>0:
            a[j]+=a[i]
            ans+=[(i+1,j+1)]
    for i in range(n,1,-1):
        ans+=[(i,i-1)]
print(len(ans))
for t in ans:print(*t)