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<iomanip>
#include<cstdio>
#include<cmath>
#include<algorithm>
#include<cstring>
#define maxn 55
using namespace std;
int n,a[maxn],b,minnum=0,pos;
bool tag;
int main()
{
	scanf("%d",&n);
	for(int i=1;i<=n;++i)
	{
	scanf("%d",&a[i]);
	if(abs(a[i])>minnum) {
		minnum=abs(a[i]);
		if(a[i]<0) tag=true;
		else tag=false;
		pos=i;
			}
	}
	if(minnum==0)
	{
		cout<<0;
		return 0;
	}
	cout<<2*n<<endl;
if(tag)   {
	cout<<pos<<' '<<1<<endl;
	cout<<pos<<' '<<1<<endl;
	for(int i=n;i>=2;--i)
	{
		cout<<1<<' '<<i<<endl;
		cout<<1<<' '<<1<<endl;
	}
return 0;
}
if(!tag)
{
	cout<<pos<<' '<<n<<endl;
	cout<<pos<<' '<<n<<endl;
	for(int i=1;i<=n-1;++i)
	{
		cout<<n<<' '<<i<<endl;
		cout<<n<<' '<<n<<endl;
	}
	return 0;
}
return 0; 
}