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.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.StringTokenizer;

public class Main {
    int n;
    int[] as;

    public static void main(String args[]) {
        new Main().run();
    }

    void run() {
        FastReader sc = new FastReader();
        n = sc.nextInt();
        as = new int[n];
        for (int i = 0; i < n; i++) {
            as[i] = sc.nextInt();
        }
        solve();
    }

    void solve() {
        ArrayList<Integer> xList = new ArrayList<>();
        ArrayList<Integer> yList = new ArrayList<>();
        int maxAbs = 0;
        int maxAbsIndex = -1;
        boolean reverseFlag = false;
        for (int i = 0; i < n; i++) {
            if (Math.abs(as[i]) > maxAbs) {
                maxAbs = as[i];
                maxAbsIndex = i;
            }
        }
        if (maxAbs == 0) {
            System.out.println(0);
            return;
        }
        if (maxAbs < 0) {
            reverseFlag = true;
            int[] bs = new int[n];
            for (int i = 0; i < n; i++) {
                bs[n - i - 1] = -as[i];
            }
            maxAbs = -maxAbs;
            maxAbsIndex = n - maxAbsIndex - 1;
        }
        boolean[] nonDec = new boolean[n - 1];
        for (int i = 0; i < n - 1; i++) {
            if (as[i] <= as[i + 1]) {
                nonDec[i] = true;
            }
        }
        for (int i = 0; i < n - 1; i++) {
            if (nonDec[i]) {
                while(as[i] > as[i + 1]) {
                    as[i + 1] += maxAbs;
                    if (reverseFlag) {
                        xList.add(n - maxAbsIndex);
                        yList.add(n - i - 1);
                    } else {
                        xList.add(maxAbsIndex + 1);
                        yList.add(i + 2);
                    }
                    if (maxAbsIndex == i + 1) {
                        maxAbs += maxAbs;
                    }
                }
            } else {
                if (maxAbs < as[i]) {
                    maxAbs = as[i];
                    if (reverseFlag) {
                        maxAbsIndex = n - i - 1;
                    } else {
                        maxAbsIndex = i;
                    }
                }
                while(as[i] > as[i + 1]) {
                    as[i + 1] += maxAbs;
                    if (reverseFlag) {
                        xList.add(n - maxAbsIndex);
                        yList.add(n - i - 1);
                    } else {
                        xList.add(maxAbsIndex + 1);
                        yList.add(i + 2);
                    }
                }
                if (maxAbs < as[i + 1]) {
                    maxAbs = as[i + 1];
                    if (reverseFlag) {
                        maxAbsIndex = n - i - 2;
                    } else {
                        maxAbsIndex = i + 1;
                    }
                }
            }
        }
        System.out.println(xList.size());
        for (int i = 0; i < xList.size(); i++) {
            System.out.println(xList.get(i) + " " + yList.get(i));
        }
    }

    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader() {
            br = new BufferedReader(new
                    InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements())
            {
                try
                {
                    st = new StringTokenizer(br.readLine());
                }
                catch (IOException e)
                {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

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

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

        double nextDouble()
        {
            return Double.parseDouble(next());
        }

        String nextLine() {
            String str = "";
            try
            {
                str = br.readLine();
            }
            catch (IOException e)
            {
                e.printStackTrace();
            }
            return str;
        }
    }
}