Language: C++

#[derive(Default)]
//NOTE
//declare variables to reduce the number of parameters for dp and dfs etc.
struct Solver {}

impl Solver {
    fn solve(&mut self) {
        let stdin = std::io::stdin();
        let mut scn = Scanner {
            stdin: stdin.lock(),
        };
        let mut s = scn.chars();
        s.insert(0, '0');
        let mut result = 0;
        let mut carry = false;
        for x in s.windows(2).rev() {
            let x1 = x[0].to_digit(10).unwrap();
            let mut x2 = x[1].to_digit(10).unwrap();
            if carry {
                x2 += 1;
            }
            carry = false;
            let y2 = 10 - x2;
            if x2 == 5 {
                if x1 >= 5 {
                    carry = true;
                    result += y2;
                } else {
                    carry = false;
                    result += x2;
                }
                continue;
            }
            if y2 < x2 {
                carry = true;
                result += y2;
            } else {
                carry = false;
                result += x2;
            }
        }
        if carry {
            result += 1;
        }
        println!("{}", result);
    }
}

fn main() {
    std::thread::Builder::new()
        .stack_size(64 * 1024 * 1024) // 64MB
        .spawn(|| {
            let mut solver = Solver::default();
            solver.solve()
        })
        .unwrap()
        .join()
        .unwrap();
}
pub mod utils {
    const DYX: [(isize, isize); 8] = [
        (0, 1),   //right
        (1, 0),   //down
        (0, -1),  //left
        (-1, 0),  //top
        (1, 1),   //down right
        (-1, 1),  //top right
        (1, -1),  //down left
        (-1, -1), //top left
    ];

    pub fn try_adj(y: usize, x: usize, dir: usize, h: usize, w: usize) -> Option<(usize, usize)> {
        let ny = y as isize + DYX[dir].0;
        let nx = x as isize + DYX[dir].1;
        if ny >= 0 && nx >= 0 {
            let ny = ny as usize;
            let nx = nx as usize;
            if ny < h && nx < w {
                Some((ny, nx))
            } else {
                None
            }
        } else {
            None
        }
    }
}

//snippet from kenkoooo
pub struct Scanner<R> {
    stdin: R,
}

impl<R: std::io::Read> Scanner<R> {
    pub fn read<T: std::str::FromStr>(&mut self) -> T {
        use std::io::Read;
        let buf = self
            .stdin
            .by_ref()
            .bytes()
            .map(|b| b.unwrap())
            .skip_while(|&b| b == b' ' || b == b'\n' || b == b'\r')
            .take_while(|&b| b != b' ' && b != b'\n' && b != b'\r')
            .collect::<Vec<_>>();
        unsafe { std::str::from_utf8_unchecked(&buf) }
            .parse()
            .ok()
            .expect("Parse error.")
    }
    pub fn read_line(&mut self) -> String {
        use std::io::Read;
        let buf = self
            .stdin
            .by_ref()
            .bytes()
            .map(|b| b.unwrap())
            .skip_while(|&b| b == b'\n' || b == b'\r')
            .take_while(|&b| b != b'\n' && b != b'\r')
            .collect::<Vec<_>>();
        unsafe { std::str::from_utf8_unchecked(&buf) }
            .parse()
            .ok()
            .expect("Parse error.")
    }
    pub fn vec<T: std::str::FromStr>(&mut self, n: usize) -> Vec<T> {
        (0..n).map(|_| self.read()).collect()
    }

    pub fn chars(&mut self) -> Vec<char> {
        self.read::<String>().chars().collect()
    }
}


Compiler output:
a.cc:1:2: error: invalid preprocessing directive #[
    1 | #[derive(Default)]
      |  ^
a.cc:126:10: error: too many decimal points in number
  126 |         (0..n).map(|_| self.read()).collect()
      |          ^~~~
a.cc:6:6: error: expected initializer before 'Solver'
    6 | impl Solver {
      |      ^~~~~~
a.cc:49:1: error: 'fn' does not name a type
   49 | fn main() {
      | ^~
a.cc:60:1: error: 'pub' does not name a type
   60 | pub mod utils {
      | ^~~
a.cc:90:1: error: 'pub' does not name a type
   90 | pub struct Scanner<R> {
      | ^~~
a.cc:94:1: error: 'impl' does not name a type
   94 | impl<R: std::io::Read> Scanner<R> {
      | ^~~~