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: $a_1 \leq a_2 \leq ... \leq a_{N}$

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.

Constraints

• $2 \leq N \leq 50$
• -$10^{6} \leq a_i \leq 10^{6}$
• All input values are integers.

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.

见题面 Input 部分

见题面 Output 部分