import java.io.InputStream;
import java.io.PrintWriter;
import java.lang.reflect.Array;
import java.math.BigDecimal;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Scanner;
import java.util.Set;
import java.util.Stack;
import java.util.TreeMap;
import java.util.TreeSet;

import static java.util.Comparator.*;

public class Main {
    public static void main(String[] args) {
        PrintWriter out = new PrintWriter(System.out);
        Solver solver = new Solver(System.in, out);
        solver.solve();
        out.close();
    }
}
class Solver {
	Scanner sc;
	PrintWriter out;
    public Solver(InputStream in, PrintWriter out) {
    	sc = new Scanner(in);
    	this.out = out;
    }
    // ==================================================================
    public void solve() {
    	int N = Integer.parseInt(sc.next());
    	int K = Integer.parseInt(sc.next());
    	long[] A = new long[N];
    	for (int i = 0; i < N; i++) {
			A[i] = Long.parseLong(sc.next());
		}
    	Arrays.sort(A);
    	long[] diff = new long[N-1];
    	for (int i = 1; i < N; i++) {
			diff[i-1] = A[i] - A[i-1];
		}
    	Arrays.sort(diff);
    	long ans = 0;
    	for (int i = 0; i < (N - 1) - (K - 1); i++) {
			ans += diff[i];
		}
    	out.println(ans);
    }
}