import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.Iterator;
import java.util.PriorityQueue;


public class Main_yukicoder324 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Printer pr = new Printer(System.out);

        n = sc.nextInt();
        int m = sc.nextInt();
        w = new int[n];
        not = new boolean[n];
        PriorityQueue<Pair> pq = new PriorityQueue<Pair>();
        for (int i = 0; i < n; i++) {
        	w[i] = sc.nextInt();
        }
        for (int i = 0; i < n; i++) {
        	pq.add(new Pair(i));
        }

        int cnt = 0;
        while (cnt < n - m) {
        	Pair e = pq.remove();
    		int l = (e.id - 1 + n) % n;
    		int r = (e.id + 1 + n) % n;

        	if ((e.le != not[l]) || (e.re != not[r])) {
        		continue;
        	}

        	not[e.id] = true;
        	cnt++;
        	if (!e.le) {
        		pq.add(new Pair(l));
        	}
        	if (!e.re) {
        		pq.add(new Pair(r));
        	}
        }

        int ret = 0;
        for (int i = 0; i < n; i++) {
        	if (!not[i]) {
        		int l = (i - 1 + n) % n;
        		int r = (i + 1 + n) % n;
        		if (!not[l]) {
        			ret += w[l];
        		}
        		if (!not[r]) {
        			ret += w[i];
        		}
        	}
        }

        pr.println(ret / 2);

        pr.close();
        sc.close();
    }

    private static int n;
    private static int[] w;
    private static boolean[] not;

    private static class Pair implements Comparable<Pair> {
    	int id;
    	int sum;
    	boolean le;
    	boolean re;

    	Pair(int id) {
    		this.id = id;
    		int l = (id - 1 + n) % n;
    		int r = (id + 1 + n) % n;
    		sum = (not[l] ? 0 : w[l]) + (not[r] ? 0 : w[id]);
    		le = not[l];
    		re = not[r];
    	}

		@Override
		public int compareTo(Pair o) {
			return Integer.compare(this.sum, o.sum);
		}
    }

    @SuppressWarnings("unused")
	private static class Scanner {
		BufferedReader br;
		Iterator<String> it;

		Scanner (InputStream in) {
			br = new BufferedReader(new InputStreamReader(in));
		}

		String next() throws RuntimeException  {
			try {
				if (it == null || !it.hasNext()) {
					it = Arrays.asList(br.readLine().split(" ")).iterator();
				}
				return it.next();
			} catch (IOException e) {
				throw new IllegalStateException();
			}
		}

		int nextInt() throws RuntimeException {
			return Integer.parseInt(next());
		}

		long nextLong() throws RuntimeException {
			return Long.parseLong(next());
		}

		float nextFloat() throws RuntimeException {
			return Float.parseFloat(next());
		}

		double nextDouble() throws RuntimeException {
			return Double.parseDouble(next());
		}

		void close() {
			try {
				br.close();
			} catch (IOException e) {
//				throw new IllegalStateException();
			}
		}
	}

	private static class Printer extends PrintWriter {
		Printer(PrintStream out) {
			super(out);
		}
	}
}