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# (Mono 4.6.2.0) (judge verdict: Runtime Error)

using System;
using System.Collections.Generic;
using System.Linq;
class Program{
	const int mod=1000000007;
	const long o=1;
	static void Main(){
		Sc sc=new Sc();
		int n=sc.I;
		long[] a=sc.La;
		long b=0,c=0;
		int q=0;
		string[] ans=new string[n*2];
		for(int i = 0;i<n;i++) {
			if(a[b]<a[i]){b=i;}
			if(a[c]>a[i]){c=i;}
		}
		if(Math.Abs(b)>Math.Abs(c)){
			for(int i = 1;i<n;i++) {
				while(a[i]<a[i-1]){
					a[i]+=a[b];
					ans[q]=(b+1)+" "+(i+1);
					q++;
					if(a[b]<a[i]){b=i;}
				}
			}
		}
		else{
			for(int i = n-2;i>=0;i--) {
				while(a[i]>a[i+1]){
					a[i]+=a[c];
					ans[q]=(c+1)+" "+(i+1);
					q++;
					if(a[c]>a[i]){c=i;}
				}
			}
		}
		Array.Resize(ref ans,q);
		Console.WriteLine("{0}",q);
		if(q>0){Console.WriteLine(String.Join("\n",ans));}
	}
}

class Sc{
	public int I{get{return int.Parse(Console.ReadLine());}}
	public long L{get{return long.Parse(Console.ReadLine());}}
	public double D{get{return double.Parse(Console.ReadLine());}}
	public string S{get{return Console.ReadLine();}}
	public int[] Ia{get{return Array.ConvertAll(Console.ReadLine().Split(),int.Parse);}}
	public long[] La{get{return Array.ConvertAll(Console.ReadLine().Split(),long.Parse);}}
	public double[] Da{get{return Array.ConvertAll(Console.ReadLine().Split(),double.Parse);}}
	public string[] Sa{get{return Console.ReadLine().Split();}}
}