Problem:
Score : 100 points

Problem Statement

There are two buttons, one of size A and one of size B.

When you press a button of size X, you get X coins and the size of that button decreases by 1.

You will press a button twice. Here, you can press the same button twice, or press both buttons once.

At most how many coins can you get?

Constraints

All values in input are integers.

3 \leq A, B \leq 20

Input

Input is given from Standard Input in the following format:

A B

Output

Print the maximum number of coins you can get.

Sample Input 1

5 3

Sample Output 1

9

You can get 5 + 4 = 9 coins by pressing the button of size 5 twice, and this is the maximum result.

Sample Input 2

3 4

Sample Output 2

7

Sample Input 3

6 6

Sample Output 3

12

Solution in Rust (1.15.1) (judge verdict: Accepted)

use std::io::stdin;
use std::io::Error;
use std::io::ErrorKind;
use std::io::Read;

#[derive(Debug)]
struct Input {
    a: u8,
    b: u8,
}

fn handle_input(input_str: String) -> Result<Input, Error> {
    let mut iter = input_str.split_whitespace();
    let input = match (iter.next(), iter.next()) {
        (Some(a_str), Some(b_str)) => {
            let (a, b): (u8, u8) = match (a_str.parse(), b_str.parse()) {
                (Ok(a), Ok(b)) => (a, b),
                _ => return Err(Error::new(ErrorKind::InvalidInput, "")),
            };
            Input { a: a, b: b }
        }
        _ => return Err(Error::new(ErrorKind::InvalidInput, "")),
    };
    Ok(input)
}

fn handle_output(input: Input) -> Result<String, Error> {
    Ok(format!(
        "{}",
        vec![
            input.a + input.a - 1,
            input.a + input.b,
            input.b + input.b - 1
        ]
        .iter()
        .max()
        .unwrap()
    ))
}

fn main() {
    let mut input_str = String::new();
    let stdin = stdin();
    stdin.lock().read_to_string(&mut input_str).unwrap();
    let input = handle_input(input_str).unwrap();
    let output = handle_output(input).unwrap();
    println!("{}", output);
}