import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        int k = sc.nextInt();
        long[] values = new long[n];
        for (int i = 0; i < n; i++) {
            values[i] = sc.nextLong();
        }
        Arrays.sort(values);
        long total = values[n - 1] - values[0];
        PriorityQueue<Long> diff = new PriorityQueue<>();
        for (int i = 0; i < n - 1; i++) {
            diff.add(values[i] - values[i + 1]);
        }
        for (int i = 0; i < k - 1; i++) {
            total += diff.poll();
        }
        System.out.println(total);
    }
}

class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}