#![allow(dead_code, deprecated, unused_variables, unused_mut)]
use std::ptr::NonNull;
fn main() {
    let s: &str = "123";
    unsafe {
        let end: NonNull<u8> = NonNull::new(s.as_ptr().cast_mut()).unwrap().add(3);
        println!("{}", end.sub(1).read() as char);
        println!("{}", end.sub(2).read() as char);
    }
}