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 (Clang 3.8.0) (judge verdict: Runtime Error)

#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <cstring>
#include <queue>
#include <stack>
#include <math.h>
#include <iterator>
#include <vector>
#include <string>
#include <set>
#include <math.h>
#include <iostream>
#include <random>
#include<map>
#include <iomanip>
#include <time.h>
#include <stdlib.h>
#include <list>
#include <typeinfo>
#include <list>
#include <set>
#include <cassert>
#include<fstream>
#include <unordered_map>
#include <cstdlib>
using namespace std;
#define Ma_PI 3.141592653589793
#define eps 0.00000001
#define LONG_INF 3000000000000000000
#define GOLD 1.61803398874989484820458
#define MAX_MOD 1000000007
#define REP(i,n) for(long long i = 0;i < n;++i)
#define seg_size 524288
int main() {
	int n;
	cin >> n;
	vector<int> a;
	REP(i, n) {
		int tmp;
		cin >> tmp;
		a.push_back(tmp);
	}
	vector<pair<int, int>> wow;
	for (int i = n - 1;i >= 1;--i) {
		if (a[i] < 0&&a[i - 1] > a[i]) {
			if (a[i - 1] + a[i] <= a[i]) {
				wow.push_back(make_pair(i + 1, i));
				a[i - 1] += a[i];
			}else if(a[i-1] + 2 * a[i] <= a[i]){
				wow.push_back(make_pair(i + 1, i));
				wow.push_back(make_pair(i + 1, i));
				a[i - 1] += 2 * a[i];
			}
		}
	}
	for (int i = 0;i < n-1;++i) {
		if (a[i] > a[i + 1]) {
			while (a[i] > a[i + 1]) {
				a[i + 1] += a[i];
				wow.push_back(make_pair(i + 1, i + 2));
			}
		}
	}
	cout << wow.size() << endl;
	for (int i = 0;i < wow.size();++i) {
		cout << wow[i].first << " " << wow[i].second << endl;
	}
	return 0;
}