#![allow(non_snake_case)]

use std::io::{ self, prelude::* };

macro_rules! pick {
    ($tokens:expr) => {
        $tokens.next().unwrap().parse().expect("parse error")
    }
}

fn main() {
    let mut s = String::new();
    io::stdin().read_to_string(&mut s).expect("i/o error");
    let mut tokens = s.split_whitespace();

    let N: usize = pick!(tokens);
    let K: usize = pick!(tokens);
    let mut A: Vec<u64> = Vec::with_capacity(N);
    for _ in 0..N {
        A.push(pick!(tokens));
    }

    A.sort();
    let mut D: Vec<_> = (0..N-1)
        .map(|i| A[i+1] - A[i])
        .collect();
    D.sort();

    let ans: u64 = D[..N-K].iter().sum();

    println!("{}", ans);
}