use std::cmp::{min};

fn main() {
    let mut nk = String::new();
    std::io::stdin().read_line(&mut nk).ok();
    let nk: Vec<usize> = nk.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let n = nk[0];
    let k = nk[1];

    if n % 2 == 0 {
        println!("{}", min(n/2, k+1));
    } else {
        println!("{}", min(n, k+1));
    }
}