import java.io.*;
import java.util.*;
public class stove {
public static void main(String[] args) throws IOException {
BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
PrintWriter pw = new PrintWriter(new OutputStreamWriter(System.out));
StringTokenizer stk = new StringTokenizer(bf.readLine());
int N = Integer.parseInt(stk.nextToken());
int K = Integer.parseInt(stk.nextToken());
int[] guests = new int[N];
for(int i = 0; i < N; i++)guests[i] = Integer.parseInt(bf.readLine());
Arrays.sort(guests);
PriorityQueue<Integer> gaps = new PriorityQueue<>();
for(int i = 0; i < N-1; i++)gaps.add(guests[i+1] - guests[i]);
int matchesusing = N;
long answer = N;
while(matchesusing != K){
answer += gaps.poll()-1;
matchesusing--;
}
System.out.println(answer);
}
}
