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 Kotlin (1.0.0) (judge verdict: Wrong Answer)

import java.util.*

class D( val n: Int, var invert: Boolean = false, val r: ArrayList<String> = ArrayList( 2 * n ) ) {
    fun addLine( x: Int, y: Int ) {
        if ( ! invert ) {
            r.add( "${x + 1} ${y + 1}" )
        } else {
            r.add( "${n - x} ${n - y}" )
        }
    }

    fun print() {
        println( r.size )
        for ( rr in r ) {
            println( rr )
        }
    }
}

fun main( args: Array<String> ) {
    val sc = Scanner( System.`in` )
    val n = sc.nextInt()
    val d = D( n )
    val a = IntArray( n, { sc.nextInt() } )
    run {
        val min = a.min()!!
        val max = a.max()!!
        if ( max < 0 || ( min < 0 && -min > max ) ) {
            d.invert = true
            a.reverse()
            for ( i in a.indices ) {
                a[i] = -a[i]
            }
        }
    }
    for ( i in a.indices ) {
        val maxI = a.indices.maxBy { a[it] }!!
        if ( a[i] < 0 ) {
            d.addLine( maxI, i )
            a[i] += a[maxI]
        }
        if ( i > 0 && a[i] < a[i - 1] ) {
            d.addLine( i - 1, i )
            a[i] += a[i - 1]
        }
    }
    d.print()
}