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 <string>
#include <vector>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <map>
#include <list>
#include <set>
#include <numeric>
#include <queue>
#include <stack>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <cstring>
#include <climits>
#include <cfloat>
#include <ctime>
#include <complex>
#include <cassert>
#include <array>
#include <bitset> 
#include <unordered_map>
#include <random>

using namespace std;
typedef long long LL;
typedef pair<int,int> P;

LL a[51];
int main() {
	int N;
	cin >> N;
	LL mx=-1e6,mn=1e6;
	int mxi,mni;
	for(int i=1;i<=N;i++){
		int a;
		cin >> a;
		if(a>mx){
			mxi=i;
			mx=a;
		}
		if(a<mn){
			mni=i;
			mn=a;
		}
	}
	cout << 2*N-2 << endl;
	if(abs(mx)>=abs(mn)){
		for(int i=1;i<=N;i++){
			if(i!=mxi){
				cout << mxi << " " << i << endl;
			}
		}
		for(int i=2;i<=N;i++){
			cout << i-1 << " " << i << endl;
		}
	}
	else{
		for(int i=1;i<=N;i++){
			if(i!=mni){
				cout << mni << " " << i << endl;
			}
		}
		for(int i=N-1;i>=1;i--){
			cout << i+1 << " " << i << endl;
		}
	}

	return 0;
}