Problem:
Score : 600 points

Problem Statement

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.

Sample Input 1

3
-2 5 -1

Sample Output 1

2
2 3
3 3

After the first operation, a = (-2,5,4).

After the second operation, a = (-2,5,8), and the condition is now satisfied.

Sample Input 2

2
-1 -3

Sample Output 2

1
2 1

After the first operation, a = (-4,-3) and the condition is now satisfied.

Sample Input 3

5
0 0 0 0 0

Sample Output 3

0

The condition is satisfied already in the beginning.

Solution in Python (3.4.3) (judge verdict: Accepted)

n=int(input())
arr=list(map(int,input().split()))
arr=[[arr[i],i+1] for i in range(n)]
mins=10**18
minpos=0
maxs=-10**18
maxpos=0
for i in range(n):
  a=arr[i][0]
  if a<mins:
    mins=a
    minpos=i+1
  if maxs<a:
    maxs=a
    maxpos=i+1
ans=[]
if maxs<=0:
  flag=False
elif mins>=0:
  flag=True
else:
  if maxs>=abs(mins):
    flag=True
    for i in range(n):
      arr[i][0]+=maxs
      ans.append([maxpos,arr[i][1]])
  else:
    flag=False
    for i in range(n):
      arr[i][0]+=mins
      ans.append([minpos,arr[i][1]])
if flag==True:
  for i in range(1,n):
    ans.append([i,i+1])
else:
  for i in range(n,1,-1):
    ans.append([i,i-1])
print(len(ans))
for i in range(len(ans)):
  print(*ans[i])