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 <iostream>
#include <algorithm>
using namespace std;

const int INF=0x3f3f3f3f;
int a[55];

int main(){
	int n,idx1,idx2;
	int MAX=-1,MIN=INF;
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		if(a[i]<MIN) {MIN=a[i];idx1=i;}
		if(a[i]>MAX) {MAX=a[i];idx2=i;}
	}
	if(abs(MAX)>=abs(MIN)){
		cout<<2*n-1<<endl;
		for(int i=1;i<=n;i++){
			cout<<idx2<<" "<<i<<endl;
		}
		for(int i=1;i<n;i++){
			cout<<i<<" "<<i+1<<endl;
		}
	}
	else{
		cout<<2*n-1<<endl;
		for(int i=1;i<=n;i++){
			cout<<idx1<<" "<<i<<endl;
		}
		for(int i=n;i>1;i--){
			cout<<i<<" "<<i-1<<endl;
		}
	}
	return 0;
}