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:
#全て0以上なら順に足していける
#全て0以下または0より大きくすればいいんじゃね？
#絶対値が最も大きいもの考えてその方向で足せば、
#全て0以下または0より大きくに統一できる(最大n-1回)
#全て0以下の場合は右から左に足す(最大n-1回)
#全て0以上の場合は左から右にたす(最大n-1回)
n=int(input())
a=list(map(int,input().split()))
c,d=min(a),max(a)
ans=[]
if abs(c)>abs(d):
    c_=a.index(c)
    for i in range(n):
        if i!=c_ and a[i]>0:
            ans.append(str(c_+1)+" "+str(i+1))
    for i in range(n-1,0,-1):
        ans.append(str(i+1)+" "+str(i))
else:
    d_=a.index(d)
    for i in range(n):
        if i!=d_ and a[i]<0:
            ans.append(str(d_+1)+" "+str(i+1))
    for i in range(n-1):
        ans.append(str(i+1)+" "+str(i+2))
l=len(ans)
print(l)
for i in range(l):
    print(ans[i])