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:
// D - Non-decreasing
#include <bits/stdc++.h>
using namespace std;
#define rp(i,s,e) for(int i=(s);i<(e);++i)
#define irp(i,s,e) for(int i=(s);i>(e);--i)

int main(){
	int N; cin>>N;
	int ix = 1, minmaxA = 0;
	rp(i, 1, N+1){
		int a; cin>>a;
		if(abs(minmaxA) < abs(a)){ minmaxA = a; ix = i; }
	}
	cout<< 2*N-1 <<endl;
	rp(i, 1, N+1) cout<< ix <<" "<< i <<endl;
	if(minmaxA<0) irp(i, N, 1) cout<< i <<" "<< i-1 <<endl;
	else rp(i, 1, N) cout<< i <<" "<< i+1 <<endl;
}