import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.Arrays;
import java.util.StringTokenizer;

public class Main {
    public static void main(String[] args) {
        final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        final BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        try {
            {
                Runner runner = new Runner(br, bw);
                runner.run();
                runner.flush();
            }
            br.close();
            bw.close();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

class Solution {
    public long solution(int nClasses, int nStudents, long[] numbers) {
        for (int i = 1; i < numbers.length; ++i) {
            numbers[i] += numbers[i - 1];
        }
        Arrays.sort(numbers);

        long sum = 0;
        int i = 0;
        while (i < nStudents) {
            sum += numbers[numbers.length - 1 - i];
            i++;
        }
        return sum;
    }
}

class Runner {
    final BufferedWriter bw;

    final int N, K;
    final long[] numbers;

    Runner(BufferedReader br, BufferedWriter bw) {
        this.bw = bw;
        var reader = new Reader(br);
        try {
            var line = reader.readInts();
            N = line[0];
            K = line[1];
            numbers = reader.readLongs();

        } catch (IOException e) {
            throw new RuntimeException(e);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public void flush() {
        try {
            bw.write('\n');
            bw.flush();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    public void run() throws IOException {
        var sol = new Solution();
        var res = sol.solution(N, K, numbers);
        _write(res);
    }

    private void _write(Object o) {
        try {
            bw.write(String.valueOf(o));
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }
}

class Reader {
    private BufferedReader br;

    public Reader(BufferedReader br) {
        this.br = br;
    }

    public int readInt() throws IOException {
        return Integer.parseInt(br.readLine());
    }

    public int[] readInts() throws IOException {
        String line = br.readLine();
        StringTokenizer st = new StringTokenizer(line, " ");
        int cnt = st.countTokens();
        int[] ints = new int[cnt];
        for (int i = 0; i < cnt; ++i) {
            ints[i] = Integer.parseInt(st.nextToken());
        }
        return ints;
    }

    public long[] readLongs() throws IOException {
        String line = br.readLine();
        StringTokenizer st = new StringTokenizer(line, " ");
        int cnt = st.countTokens();
        long[] longs = new long[cnt];
        for (int i = 0; i < cnt; ++i) {
            longs[i] = Long.parseLong(st.nextToken());
        }
        return longs;
    }
}