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 <bits/stdc++.h>
using namespace std;

#define maxn 200005
typedef long long ll;
typedef double db;

int n, k;
int a[maxn];
int b[maxn];

typedef pair<int, int> pii;
vector<pii> ans;
multiset<pii> s;
multiset<pii> aux;

int printAns(int i) {

	//cout << i << endl;

	for (int j = i - 1; j > 0; j--)
		ans.push_back(make_pair(j, j - 1));
	for (int j = i; j < n - 1; ++j)
		ans.push_back(make_pair(j, j + 1));

	if (ans.size() > 2 * n)
		return 0;

	//cout << i << endl;

	cout << ans.size() << endl;
	for (unsigned int i = 0; i < ans.size(); ++i)
		cout << ans[i].first + 1 << ' ' << ans[i].second + 1 << endl;
	return 1;
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);

	cin >> n;
	for (int i = 0; i < n; ++i) {
		cin >> a[i];
		s.insert(make_pair(a[i], i));
	}

	multiset<pii>::iterator iter;
	iter = s.end();
	iter--;
	if ((*s.begin()).first >= 0) {
		cout << n - 1 << endl;
		for (int i = 0; i < n - 1; ++i)
			cout << i + 1 << ' ' << i + 2 << endl;
	} else if ((*iter).first <= 0) {
		cout << n - 1 << endl;
		for (int i = n - 1; i > 0; i--)
			cout << i + 1 << ' ' << i << endl;
	} else {
		for (int i = 0; i < n + 1; ++i) {
			ans.clear();
			aux.clear();
			copy(a, a + n, b);
			for (multiset<pii>::iterator iter = s.begin(); iter != s.end();
					iter++) {
				//cout << (*iter).first << ' ' << (*iter).second << endl;
				aux.insert(make_pair((*iter).first, (*iter).second));
			}
			for (int j = 0; j < n; ++j) {
				if (j < i && b[j] > 0) {
					multiset<pii>::iterator iter = aux.begin();
					int	mini = (*iter).first;
					int posMini = (*iter).second;
					int tmp = floor(-b[j] / db(mini));
					if (ans.size() + tmp > 2 * n)
						break;
					int ol = b[j];
					int ne = b[j] + tmp * mini;
					b[j] = ne;
					aux.erase(make_pair(ol, j));
					aux.insert(make_pair(ne, j));
					for (int k = 0; k < tmp; ++k)
						ans.push_back(make_pair(posMini, j));
				} else if (j >= i && b[j] < 0) {
					multiset<pii>::iterator iter = aux.end();
					iter--;
					int	maxi = (*iter).first;
					int posMaxi = (*iter).second;
					//cout << i << ' ' << j << ' ' << maxi << ' ' << posMaxi << endl;
					int tmp = ceil(-b[j] / db(maxi));
					if (ans.size() + tmp > 2 * n)
						break;
					int ol = b[j];
					int ne = b[j] + tmp * maxi;
					b[j] = ne;
					aux.erase(make_pair(ol, j));
					aux.insert(make_pair(ne, j));
					for (int k = 0; k < tmp; ++k)
						ans.push_back(make_pair(posMaxi, j));
				}
				if (j == n - 1 && printAns(i))
					return 0;
			}
		}
	}

	return 0;
}