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 C# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
using System.Linq;
using System.Collections.Generic;
using static System.Console;
using System.Text;
using System.IO;
using static System.Math;
using System.Numerics;

namespace AtCoder
{
    class Program
    {
        static public long[] Sarray() { return ReadLine().Split().Select(long.Parse).ToArray(); }
        static public List<long> Slist() { return ReadLine().Split().Select(long.Parse).ToList(); }
        static long Mod = (long)1e9 + 7;
        static void Main(string[] args)
        {
            SetOut(new StreamWriter(OpenStandardOutput()) { AutoFlush = false });
            Solve();
            Out.Flush();
            Read();
        }
        static void Solve()
        {
            var N = Sarray()[0];
            var ai = Sarray();
            var pre = true;
            var bp = ai.Max();
            if (ai.Max() + ai.Min() < 0)
            {
                pre = false;
                bp = ai.Min();
            }
            var bi = 0;
            var ansStrings = new List<string>();
            for (var i = 0; i < N; ++i)
                if (ai[i] == bp)
                    bi = i;
            if (pre)
            {
                for (var i = 0; i < N; ++i)
                {
                    ansStrings.Add($"{bi + 1} {i + 1}");
                    if (ai[i] < 0)
                        ansStrings.Add($"{bi + 1} {i + 1}");
                    bi = i;
                }
            }
            else
            {
                for (int i = (int)N - 1; 0 <= i; --i)
                {
                    ansStrings.Add($"{bi + 1} {i + 1}");
                    if (0 < ai[i])
                        ansStrings.Add($"{bi + 1} {i + 1}");
                    bi = i;
                }
            }
            WriteLine(ansStrings.Count);
            foreach (var a in ansStrings)
                WriteLine(a);
        }
    }
}