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: Accepted)

import Data.List

main = do
  n <- (read :: String -> Int) <$> getLine
  input <- map (read :: String -> Int) . words <$> getLine
  let max = maximum input
      min = minimum input
  solve min max input

increase :: Int -> [[Int]]
increase n = [[a, a+1] | a <- [1..n-1]]

decrease :: Int -> [[Int]]
decrease n = reverse [[a+1, a] | a <- [1..n-1]]

makeList :: Int -> Int -> [[Int]]
makeList n m = [[m, a] | a <- [1..n], a /= m]

solve :: Int -> Int -> [Int] -> IO ()
solve min max s
  | min >= 0          = do
    print (length s - 1)
    putStr . toString . increase $ length s
  | max <= 0          = do
    print (length s - 1)
    putStr . toString . decrease $ length s
  | abs min < abs max = do
    let maxIndex = (+1) . head . elemIndices max $ s
    print $ (length s - 1) * 2
    putStr $ toString $ makeList (length s) maxIndex
    putStr . toString . increase $ length s
  | otherwise         = do
    let minIndex = (+1) . head . elemIndices min $ s
    print $ (length s - 1) * 2
    putStr $ toString $ makeList (length s) minIndex
    putStr . toString . decrease $ length s

toString :: [[Int]] -> String
toString = unlines . map (unwords . map show)