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<cstdio>
#include<cstdlib>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<queue>
using namespace std;
int a[100];	int n;
pair<int,int>Out[1500];
int main(){
	scanf("%d",&n);
	for(int i=1;i<=n;i++) scanf("%d",&a[i]);
	int mx=-(1<<30);int mn=(1<<30);int pm,pn;
	for(register int i=1;i<=n;i++)
		if(a[i]>mx)	mx=a[i],pm=i;
	for(register int i=1;i<=n;i++)
		if(a[i]<mn) mn=a[i],pn=i;
	if(a[pm]+a[pn]>0){
		printf("%d\n",2*n);
		printf("%d %d\n",pm,1);
			printf("%d %d\n",pm,1);
			for(int i=1;i<n;i++){
				printf("%d %d\n%d %d\n",i,i+1,i,i+1);
			}		
	}
	else {
		printf("%d\n",2*n);
		printf("%d %d\n",pn,n);
		printf("%d %d\n",pn,n);
			for(int i=n-1;i>=1;i--){
				printf("%d %d\n%d %d\n",i+1,i,i+1,i);
			}	
	}
	return 0;
}