use std::{collections::{BTreeMap, BinaryHeap}, cmp::Reverse};


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];
    let mut a = String::new();
    std::io::stdin().read_line(&mut a).ok();
    let a: Vec<usize> = a.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();

    let mut result = 0usize;
    let mut minidx = n;
    let mut a = a.into_iter().skip(1).enumerate().collect::<Vec<(usize, usize)>>();
    a.sort_by_key(|&(i, v)| (Reverse(v), i%2, i));
    for i in 0..k-1 {
        let (idx, val) = a[i];
        minidx = idx.min(minidx);
        result += val;
    }
    for i in k-1..n-1 {
        let (idx, val) = a[i];
        let minidx = idx.min(minidx);
        if minidx % 2 == 0 {
            result += val;
            break;
        }
    }
    println!("{}", result);
}