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: Wrong Answer)

#include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <cstdio>
#include <functional>
#include <set>
#include <queue>
#include <cctype>
#include <climits>
#include <stack>
#include <map>
#include <cstring>
#include <cassert>
 
using namespace std;

int main(){

	int n;
	cin>>n;

	vector<long long> a(n);
	long long mi=10000000,ma=-10000000;
	int mii,mai;
	for(int i=0;i<n;i++){
		cin>>a[i];
		if(mi>a[i]) mi=a[i],mii=i;
		if(ma<a[i]) ma=a[i],mai=i;
	}
	cout<<mii<<" "<<mai<<endl;
	vector<int> res;
	if(abs(ma)>=abs(mi)){
		for(int i=0;i<n;i++){
			a[i]+=a[mai];
			res.push_back(mai);
			res.push_back(i);
		}
		for(int i=0;i<n-1;i++){
			a[i+1]+=a[i];
			res.push_back(i);
			res.push_back(i+1);
		}
	}else{
		for(int i=0;i<n;i++){
			a[i]+=a[mii];
			res.push_back(mai);
			res.push_back(i);
		}
		for(int i=n-1;i>0;i--){
			a[i-1]+=a[i];
			res.push_back(i);
			res.push_back(i-1);
		}		
	}

//	for(int i=0;i<n;i++) cout<<a[i]<<" ";
//	cout<<endl;

	cout<<res.size()/2<<endl;
	for(int i=0;i<res.size();i+=2){
		cout<<res[i]+1<<" "<<res[i+1]+1<<endl;
	}


	return 0;
}