fn hor_mirror(s: String) -> String {
    let bytes = s.into_bytes();

    let slices: Vec<&[u8]> = bytes.split(|b| b == &b'\n').rev().collect();

    let mut s = Vec::with_capacity(bytes.len());

    for slice in slices {
        s.extend_from_slice(slice);
        s.push(b'\n');
    }
    s.pop();
    String::from_utf8(s).unwrap()
}

fn vert_mirror(s: String) -> String {
    let mut bytes = s.into_bytes();
    for line in bytes.split_mut(|b| b == &b'\n') {
        line.reverse();
    }
    String::from_utf8(bytes).unwrap()

}
// first parameter: dots have to be replaced by function of one variable
fn oper<F: Fn(String) -> String>(f: F, s: String) -> String {
    f(s)
}