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

import java.util.*;
import java.io.*;
 
public class Main {
    public static void main(String[] args) throws Exception {
        FastScanner sc = new FastScanner(System.in);
        PrintWriter pw = new PrintWriter(System.out);
        StringBuilder sb = new StringBuilder();
        int n = sc.nextInt();
        int[] a = sc.nextIntArray(n);
        int max = 0;
        int maxi = 1;
        int min = 0;
        int mini = 1;
        for(int i = 0; i < n; i++){
            if(a[i] < 0){
                if(min < Math.abs(a[i])){
                    min = Math.abs(a[i]);
                    mini = i+1;
                }
            }else{
                if(max < a[i]){
                    max = a[i];
                    maxi = i+1;
                }
            }
        }
        if(max >= min){
            int cnt = n-1;
            for(int i = 0; i < n; i++){
                if(maxi == i+1){
                    continue;
                }
                a[i] += max;
                sb.append(maxi).append(" ").append(i+1).append("\n");
            }
            for(int i = 0; i < n-1; i++){
                if(a[i] > a[i+1]){
                    cnt++;
                    a[i+1] += a[i];
                    sb.append(i+1).append(" ").append(i+2).append("\n");
                }
            }
            pw.println(cnt);
            pw.print(sb.toString());
        }else{
            int cnt = n-1;
            for(int i = 0; i < n; i++){
                if(mini == i+1){
                    continue;
                }
                a[i] -= min;
                sb.append(mini).append(" ").append(i+1).append("\n");
            }
            for(int i = 0; i < n-1; i++){
                if(a[i] > a[i+1]){
                    cnt++;
                    a[i] += a[i+1];
                    sb.append(i+2).append(" ").append(i+1).append("\n");
                }
            }
            pw.println(cnt);
            pw.print(sb.toString());
        }
        pw.flush();
    }
    
    static class GeekInteger {
        public static void save_sort(int[] array) {
            shuffle(array);
            Arrays.sort(array);
        }
 
        public static int[] shuffle(int[] array) {
            int n = array.length;
            Random random = new Random();
            for (int i = 0, j; i < n; i++) {
                j = i + random.nextInt(n - i);
                int randomElement = array[j];
                array[j] = array[i];
                array[i] = randomElement;
            }
            return array;
        }
 
    }
}

class Point{
    int now,cnt;
    public Point(int n, int c){
        this.now = n;
        this.cnt = c;
    }
}

class FastScanner {
    private BufferedReader reader = null;
    private StringTokenizer tokenizer = null;
    public FastScanner(InputStream in) {
        reader = new BufferedReader(new InputStreamReader(in));
        tokenizer = null;
    }

    public String next() {
        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                tokenizer = new StringTokenizer(reader.readLine());
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken();
    }

    public String nextLine() {
        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
            try {
                return reader.readLine();
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        }
        return tokenizer.nextToken("\n");
    }

    public long nextLong() {
        return Long.parseLong(next());
    }

    public int nextInt() {
        return Integer.parseInt(next());
    }

    public double nextDouble() {
         return Double.parseDouble(next());
    }
    
    public String[] nextArray(int n) {
        String[] a = new String[n];
        for (int i = 0; i < n; i++)
            a[i] = next();
        return a;
    }

    public int[] nextIntArray(int n) {
        int[] a = new int[n];
        for (int i = 0; i < n; i++)
            a[i] = nextInt();
        return a;
    }

    public long[] nextLongArray(int n) {
        long[] a = new long[n];
        for (int i = 0; i < n; i++)
            a[i] = nextLong();
        return a;
    } 
}