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 Go (1.6) (judge verdict: Wrong Answer)

package main

import (
	"bufio"
	"fmt"
	"log"
	"os"
	"strconv"
)

// const abcd = "abcdefghijklmnopqrstuvwxyz"
// const ABCD = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
// var dx = [...]int{0, 1, 0, -1, 1, -1, -1, 1}
// var dy = [...]int{1, 0, -1, 0, 1, 1, -1, -1}
// var inf int = 1e13

// var mod = 1000000007
var next = newScanner()

// ---------------------------------------------------------

func main() {
	log.SetFlags(log.Lshortfile)
	N := next.Int()
	a := next.Ints(N)
	ans := make([]Pair, 0)
	next := 1
RESTART:
	plusIndex := -1
	minusIndex := -1
	for i := 0; i < N; i++ {
		if a[i] < 0 {
			minusIndex = i
			break
		}
	}
	for i := N - 1; i >= 0; i-- {
		if a[i] > 0 {
			plusIndex = i
			break
		}
	}
	for i := next; i < N; i++ {
		next = i
		for a[i] < a[i-1] {
			// log.Println(a[i], a[i-1])
			if plusIndex != -1 {
				a[i] += a[plusIndex]
				ans = append(ans, Pair{i, plusIndex})
				if i == minusIndex && a[i] > 0 {
					goto RESTART
				}
			} else if minusIndex != -1 {
				a[i-1] += a[minusIndex]
				ans = append(ans, Pair{i - 1, minusIndex})
				if i == plusIndex && a[i] < 1 {
					goto RESTART
				}
			} else {
				// log.Println("ERRROR", plusIndex, minusIndex)
				// log.Println(a)
			}
			// log.Println(a)
		}
	}
	log.Println(a)
	fmt.Println(len(ans))
	for i := 0; i < len(ans); i++ {
		fmt.Println(ans[i].b+1, ans[i].a+1)
	}
}

// ---------------------------------------------------------

// // Pair is...
type Pair struct {
	a, b int
}

//
// // Pairs is sorted by []Pair struct
// type Pairs []Pair
//
// func (p Pairs) Len() int {
// 	return len(p)
// }
// func (p Pairs) Swap(i, j int) {
// 	p[i], p[j] = p[j], p[i]
// }
//
// func (p Pairs) Less(i, j int) bool {
// 	if p[i].a < p[j].a {
// 		return true
// 	} else if p[i].a == p[j].a {
// 		return p[i].b < p[j].b
// 	}
// 	return false
// }

// ------int method-------------------------
func in(c, a, z int) bool {
	return c >= a && c < z
}
func btoi(b bool) int {
	if b {
		return 1
	}
	return 0
}
func itob(a int) bool {
	if a == 0 {
		return false
	}
	return true
}
func max(a ...int) int {
	r := a[0]
	for i := 0; i < len(a); i++ {
		if r < a[i] {
			r = a[i]
		}
	}
	return r
}
func min(a ...int) int {
	r := a[0]
	for i := 0; i < len(a); i++ {
		if r > a[i] {
			r = a[i]
		}
	}
	return r
}
func sum(a []int) int {
	r := 0
	for i := 0; i < len(a); i++ {
		r += a[i]
	}
	return r
}
func pro(a []int) int {
	r := 1
	for i := 0; i < len(a); i++ {
		r *= a[i]
	}
	return r
}
func fill(a []int, n int) []int {
	for i := 0; i < len(a); i++ {
		a[i] = n
	}
	return a
}
func minmax(a, b int) (int, int) {
	if a > b {
		return b, a
	}
	return a, b
}
func abs(a int) int {
	if a < 0 {
		return -a
	}
	return a
}

// ---------- buffered scanner -----------------------------------------
func iferr(err error) {
	if err != nil {
		panic(err)
	}
}

type scanner struct {
	r   *bufio.Reader
	buf []byte
	p   int
}

func newScanner() *scanner {
	rdr := bufio.NewReaderSize(os.Stdin, 10000)
	return &scanner{r: rdr}
}
func (s *scanner) next() string {
	s.pre()
	start := s.p
	for ; s.p < len(s.buf); s.p++ {
		if s.buf[s.p] == ' ' {
			break
		}
	}
	result := string(s.buf[start:s.p])
	s.p++
	return result
}
func (s *scanner) Line() string {
	s.pre()
	start := s.p
	s.p = len(s.buf)
	return string(s.buf[start:])
}
func (s *scanner) String() string {
	return s.next()
}
func (s *scanner) Int() int {
	v, e := strconv.Atoi(s.next())
	iferr(e)
	return v
}
func (s *scanner) Ints(n int) []int {
	r := make([]int, n)
	for i := 0; i < n; i++ {
		r[i] = s.Int()
	}
	return r
}
func (s *scanner) Int64() int64 {
	v, e := strconv.ParseInt(s.next(), 10, 64)
	iferr(e)
	return v
}
func (s *scanner) Uint64() uint64 {
	v, e := strconv.ParseUint(s.next(), 10, 64)
	iferr(e)
	return v
}
func (s *scanner) Float64() float64 {
	v, e := strconv.ParseFloat(s.next(), 64)
	iferr(e)
	return v
}
func (s *scanner) pre() {
	if s.p >= len(s.buf) {
		s.readLine()
		s.p = 0
	}
}
func (s *scanner) readLine() {
	s.buf = make([]byte, 0)
	for {
		l, p, e := s.r.ReadLine()
		iferr(e)
		s.buf = append(s.buf, l...)
		if !p {
			break
		}
	}
}