100813: [AtCoder]ABC081 D - Non-decreasing

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.