Problem: 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.

Examples

Input

3
-2 5 -1


Output

2
2 3
3 3


Input

2
-1 -3


Output

1
2 1


Input

5
0 0 0 0 0


Output

0

Solution (in CPP):

Solution:
#include <bits/stdc++.h>

#define F first
#define S second

using namespace std;

typedef long long LL;
typedef pair<int, int> PII;

const int N = 55, M = 8010, INF = 0x3f3f3f3f;

int n;
int a[N];
vector<PII> res;

void add(int x, int u)
{
	for (int i = 1; i <= n; i ++ )
	{
		a[i] += x;
		res.push_back({u, i});
	}
}

int main()
{
	cin >> n;
	int maxa = -INF, axi, mina = INF, ini;
	for (int i = 1; i <= n; i ++ )
	{
		cin >> a[i];
		if (a[i] > maxa) maxa = a[i], axi = i;
		if (a[i] < mina) mina = a[i], ini = i;
	}
	
	if (abs(maxa) > abs(mina)) add(maxa, axi);
	else add(mina, ini);
	
	if (a[1] > 0)
	{
		for (int i = 1; i < n; i ++ ) res.push_back({i, i + 1});
	}
	else
	{
		for (int i = n; i > 1; i -- ) res.push_back({i, i - 1});
	}
	
	cout << res.size() << endl;
	for (auto u : res) cout << u.F << ' ' << u.S << endl;
	
	return 0;
}