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;

fn main() {
    let mut s = String::new();

    io::stdin().read_line(&mut s)
        .expect("Failed to read line");

    let numbers: Vec<i32> =
        s.split(' ').map(|s| s.trim())
        .filter(|s| !s.is_empty())
        .map(|s| s.parse().unwrap())
        .collect();

    let a = numbers[0];
    let b = numbers[1];

    if a > b {
        println!("{}", 2 * a - 1);
    } else if a < b {
        println!("{}", 2 * b - 1);
    } else {
        println!("{}", a + b);
    }
}