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 (1.15.1) (judge verdict: Wrong Answer)

use std::io::*;
use std::str::FromStr;
// use std::collections::BTreeSet;
// use std::collections::HashMap;

fn read<T: FromStr>() -> T {
    let stdin = stdin();
    let stdin = stdin.lock();
    let token: String = stdin
        .bytes()
        .map(|c| c.expect("failed to read char") as char) 
        .skip_while(|c| c.is_whitespace())
        .take_while(|c| !c.is_whitespace())
        .collect();
    token.parse().ok().expect("failed to parse token")
}


fn main() {
    let n: u32 = read();
    let mut ai: Vec<i32> = (0..n).map(|_| read()).collect();
    // let uniq: BTreeSet<u32> = ai.iter().cloned().collect();

    let mut max: i32 = ai[0];
    let mut argmax: u32 = 0;
    let mut min: i32 = ai[0];
    let mut argmin: u32 = 0;
    for i in 0..n {
        if max < ai[i as usize] {
            max = ai[i as usize];
            argmax = i;
        }
        if min > ai[i as usize] {
            min = ai[i as usize];
            argmin = i;
        }
    }

    let mut msgs = Vec::new();
    if max > 0 {
        for i in 0..n-1 {
            // let a = ai.iter().nth(i as usize).unwrap();
            let j = (i + 1) as usize;
            let a = ai[i as usize];
            let mut b = ai[j];
            while a > b {
                ai[j] = b + max;
                b = ai[j];
                let msg = format!("{} {}", argmax + 1, j + 1);
                msgs.push(msg);
                if i + 1 == argmax {
                    if max < b {
                        max = b;
                        argmax = i + 1;
                    }
                }
            }
        }
    } else {
        for i in (1..n).rev() {
            let j = (i - 1) as usize;
            let a = ai[i as usize];
            let mut b = ai[j];
            while b > a {
                ai[j] = b + min;
                b = ai[j];
                let msg = format!("{} {}", argmin + 1, j + 1);
                msgs.push(msg);
                if i - 1 == argmin {
                    if min < b {
                        min = b;
                        argmin = i - 1;
                    }
                }
            }
        }
    }
    
    println!("{}", msgs.iter().count());
    for msg in msgs.iter() {
        println!("{}", msg);
    }

    println!("{:?}", ai);
}