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 Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.*;


public class Main {
    static void solve() {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();

        ArrayList<Integer> a = new ArrayList<>();
        int min = 0;
        int max = 0;
        int minIndex = 0;
        int maxIndex = 0;
        for(int i = 0; i < n; i++){
            int na = sc.nextInt();
            if (na < min) {
                min = na;
                minIndex = i;
            }else if(na > max) {
                max = na;
                maxIndex = i;
            }
            a.add(na);
        }
        ArrayList<String> ans = new ArrayList<>();

        if(Math.abs(max) > Math.abs(min)){
            for(int i = 0; i < n; i++){
                if(a.get(i) < 0){
                    ans.add(String.valueOf(maxIndex+1) + " " + String.valueOf(i+1));
                }
            }
            for(int i = 0; i < n-1; i++){
                ans.add(String.valueOf(i+1) + " " + String.valueOf(i+2));
            }
        }else if(Math.abs(max) < Math.abs(min)){
            for(int i = 0; i < n; i++){
                if(a.get(i) > 0){
                    ans.add(String.valueOf(minIndex+1) + " " + String.valueOf(i+1));
                }
            }
            for(int i = n-1; i >= 0; i--){
                ans.add(String.valueOf(i+2) + " " + String.valueOf(i+1));
            }
        }

        System.out.println(ans.size());
        for(String s : ans){
            System.out.println(s);
        }
    }

    public static void main(String[] args) {
        solve();
    }
}