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>
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
#define SIZE 200005
#define INF 1000000005LL
#define MOD 1000000007

using namespace std;
typedef long long int ll;
typedef pair <int,int> P;

int N;
int a[SIZE];
ll K;

int main()
{
	cin >> N;
	int amin = INF,amax=-INF;
	int argmin,argmax;
	rep(i,0,N){
		cin >> a[i];
		if(amin > a[i]){
			amin = a[i];
			argmin = i;
		}
		if(amax < a[i]){
			amax = a[i];
			argmax = i;
		}
	}
	cout << (N-1)*2 << endl;
	if(abs(amax) >= abs(amin)){
		rep(i,0,N) if(i != argmax){
			cout << argmax+1 << " " << i+1 << endl;
		}
		rep(i,0,N-1){
			cout << i+1 << " " << i+1+1 << endl;
		}
	}else{
		rep(i,0,N) if(i != argmin){
			cout << argmin+1 << " " << i+1 << endl;
		}
		rep(i,0,N-1){
			cout << N-i << " " << N-i-1 << endl;
		}
	}


	return 0;
}