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>
using namespace std;
#define ll long long
const ll MOD = 1000000007;

int main(){
	int N, a;
	cin >> N;
	int mn = MOD, mx = -MOD, mni = 0, mxi = 0;
	for (int i = 0;i < N;i++) {
		cin >> a;
		if (mn > a) mn = a, mni = i;
		if (mx < a) mx = a, mxi = i;
	}
	if (mn >= 0) {
		cout << N - 1 << endl;
		for (int i = 1;i < N;i++)
			cout << i << " " << i + 1 << endl;
	}
	else if (mx <= 0) {
		cout << N - 1 << endl;
		for (int i = N;i > 1;i--)
			cout << i << " " << i - 1 << endl;
	}
	else if (-mn > mx) {
		cout << N * 2 - 2 << endl;
		for (int i = 0;i < N;i++) {
			if (i != mni) cout << mni + 1 << " " << i + 1 << endl;
		}
		for (int i = N;i > 1;i--) {
			cout << i << " " << i - 1 << endl;
		}
	}
	else {
		cout << N * 2 - 2 << endl;
		for (int i = 0;i < N;i++) {
			if (i != mxi) cout << mxi + 1 << " " << i + 1 << endl;
		}
		for (int i = 1;i < N;i++) {
			cout << i << " " << i + 1 << endl;
		}
	}
}