module Main;

import CPLib.IO;

main: IO ();
main = (
    let (n, k) = (*read_i, *read_i);
    let p = *read_is(n);
    let (ans, p) = loop(
        ([], p), |(ans, p)|
        let size_before = ans.@size;
        let (ans, p) = range(0, n-k).fold(
            (ans, p), |i, (ans, p)|
            if p.@(i) < p.@(i+k) { (ans, p) };
            let ans = ans.push_back((i, i+k));
            let v1 = p.@(i);
            let v2 = p.@(i+k);
            let p = p.set(i, v2).set(i+k, v1);
            (ans, p)
        );
        let size_after = ans.@size;
        if size_before == size_after { break $ (ans, p) };
        continue $ (ans, p)
    );
    let sorted = range(0, n-1).check_all(|i| p.@(i) < p.@(i+1));
    if !sorted {
        println $ "-1"
    } else {
        println $ ans.@size.to_string;;
        ans.to_iter.map(|(a, b)|
            "{} {}\n".format((a+1, b+1))
        ).concat_iter.println
    }
);