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 Rust (1.42.0) (judge verdict: Accepted)

use proconio::input;

fn main() {
    input!(n: usize, mut a: [i32; n]);
    let c = a
        .iter()
        .enumerate()
        .max_by_key(|(_, &x)| x.abs())
        .unwrap()
        .0;
    let ac = a[c];
    let mut ans = vec![];
    let mut mv = |i, j| {
        ans.push((i, j));
        a[j] += a[i];
    };
    for i in (0..n).filter(|&i| i != c) {
        mv(c, i);
    }
    if 0 <= ac {
        for i in 0..n - 1 {
            mv(i, i + 1);
        }
    } else {
        for i in (0..n - 1).rev() {
            mv(i + 1, i);
        }
    }
    println!("{}", ans.len());
    for (x, y) in ans {
        println!("{} {}", x + 1, y + 1);
    }
}