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 Haskell (GHC 7.10.3) (judge verdict: Wrong Answer)

{-# LANGUAGE MultiWayIf #-}

import Data.List (minimumBy)

showIs is it = show is++" "++show it

solveSimple [] _ = []
solveSimple ((a,i):as) (maxA,maxI) = showIs maxI i:solveSimple as (a+maxA,i)

solveRev [] _ = []
solveRev ((a,i):rs) (minA,minI) = showIs minI i:solveRev rs (a+minA,i)


main :: IO ()
main = do
  n <- read <$> getLine :: IO Int
  as <- map read.words <$> getLine :: IO [Int]
  let ais = zip as [1..] :: [(Int,Int)]
      (maxA,maxI) = maximum ais
      (minA,minI) = minimum ais
      ans = if | minA >= 0 -> solveSimple ais (maxA, maxI)
               | maxA < 0 -> solveRev (reverse ais) (minA, minI)
               | abs maxA >= abs minA ->
                  [showIs maxI i|(a,i)<-ais, a<0] ++
                  solveSimple (map (\(a,i)->if a < 0 then (a+maxA,i) else (a,i)) ais) (maxA, maxI)
               | otherwise ->
                  [showIs minI i|(a,i)<-ais, a>0] ++
                  solveRev (map (\(a,i)->if a >= 0 then (a+minA,i) else (a,i)) ais) (minA, minI)
  print $ length ans
  putStr $ unlines ans