Problem:
Score : 600 points

Problem Statement

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.

Sample Input 1

3
-2 5 -1

Sample Output 1

2
2 3
3 3

After the first operation, a = (-2,5,4).

After the second operation, a = (-2,5,8), and the condition is now satisfied.

Sample Input 2

2
-1 -3

Sample Output 2

1
2 1

After the first operation, a = (-4,-3) and the condition is now satisfied.

Sample Input 3

5
0 0 0 0 0

Sample Output 3

0

The condition is satisfied already in the beginning.

Solution in Perl (v5.18.2) (judge verdict: Accepted)

$N = <STDIN>+0;
@A=split " ",<STDIN>;


$max=$A[0];$min=$A[0];$maxi=0;$mini=0;
for($i=1;$i<=$#A;$i++){
	if($max<$A[$i]) { $max=$A[$i];$maxi=$i; }
	if($min>$A[$i]) { $min=$A[$i];$mini=$i; }
}

$,=" ";
$\="\n";
$k=0;

if($max*$min<0) {
	print $#A*2;
	if($max>=-$min) {
		for($i=0;$i<=$#A;$i++){
			next if ($i==$maxi);
			print $maxi+1,$i+1;
		}
		for($i=0;$i<=$#A-1;$i++) {
			print $i+1,$i+2;
		}
	} else {
		for($i=0;$i<=$#A;$i++){
			next if ($i==$mini);
			print $mini+1,$i+1;
		}
		for($i=$#A;$i>=1;$i--) {
			print $i+1,$i;
		}
	}
} elsif( $min>=0 ) {
	print $#A;
	for($i=0;$i<=$#A-1;$i++) {
		print $i+1,$i+2;
	}
} elsif ($max<=0) {
	print $#A;
	for($i=$#A;$i>=1;$i--) {
		print $i+1,$i;
	}
}