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;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < n; i++)
#define rrep(i, n, m) for (int i = n; i >= m; i--)

int main(){
	int n;
	int a[50];

	cin >> n;
	rep(i, n) cin >> a[i];

	auto min_it = min_element(a, a+n);
	auto max_it = max_element(a, a+n);
	int min_pos = distance(a, min_it);
	int max_pos = distance(a, max_it);
	int min = *min_it;
	int max = *max_it;

	bool mmode = false;

	int pos;
	if(abs(min) > abs(max)){
		mmode = true;
		pos = min_pos;
	}else{
		pos = max_pos;
	}

	cout << 2*n-2 << endl;

	rep(i, n) {
		if(i==pos) continue;

		cout << pos+1 << " " << i+1 << endl;
	}

	if(mmode == false){
		rep(i, n-1) cout << i+1 << " " << i+2 << endl;
	}else{
		rrep(i, n-1, 1) cout << i+1 << " " << i << endl;
	}
	
	
}