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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<climits>
#include<iostream>
#include<sstream>
#include<utility>
#include<map>
#include<vector>
#include<queue>
#include<algorithm>
#include<set>
#include<stack>
#include<functional>
using namespace std;
typedef long long ll;
typedef pair<int,int>P;

int main()
{
	int N,mnp=0,mxp=0;
	ll mn=10000000,mx=-10000000;
	vector<ll> V;
	vector<P> res;
	cin>>N;
	for(int i=0;i<N;i++)
	{
		ll t;
		cin>>t;
		if(mn>t)
		{
			mn=t;
			mnp=i;
		}
		if(mx<t)
		{
			mx=t;
			mxp=i;
		}
		V.push_back(t);
	}
	if(abs(mn)>abs(mx))
	{
		for(int i=0;i<N;i++)
		{
			if(V[i]>0)
			{
				res.push_back(make_pair(mnp,i));
				V[i]+=mn;
			}
		}

		for(int i=N-1;i>0;i--)
		{
			if(V[i-1]>V[i])
			{
				res.push_back(make_pair(i,i-1));
				V[i-1]+=V[i];
			}
		}
	}
	else
	{
		for(int i=0;i<N;i++)
		{
			if(V[i]<0)
			{
				res.push_back(make_pair(mxp,i));
				V[i]+=mx;
			}
		}
		for(int i=1;i<N;i++)
		{
			if(V[i-1]>V[i])
			{
				res.push_back(make_pair(i-1,i));
				V[i]+=V[i-1];
			}
		}
	}
	cout<<res.size()<<endl;
	for(int i=0;i<res.size();i++)
		cout<<res[i].first+1<<" "<<res[i].second+1<<endl;
}