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

public class clearing_mb {
    static double solveGivenStart(double[][] areas, double[] c, int nPosts, int start, double[] dp) {
        Arrays.fill(dp, Double.POSITIVE_INFINITY);
        dp[start] = 0;
        int n = c.length;
        for (int p = 2; p <= nPosts; ++p) {
            int minPrevIdx = start + p - 2;
            for (int i = n - 1; i > minPrevIdx; --i) {
                double curr = Double.POSITIVE_INFINITY;
                double[] areasEndingHere = areas[i];
                for (int prev = minPrevIdx; prev < i; ++prev) {
                    curr = Math.min(curr, dp[prev] + areasEndingHere[prev]);
                }
                dp[i] = curr;
            }
        }
        double result = Double.POSITIVE_INFINITY;
        for (int i = start + nPosts - 1; i < n; ++i) {
            result = Math.min(result, dp[i] + areas[start][i]);
        }
        return result;
    }

    static double solve(double[] c, int p) {
        int n = c.length;
        double[][] areas = new double[n][n];
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j < n; ++j) {
                double diff = c[i] - c[j];
                if (diff < 0) {
                    diff += Math.PI * 2;
                }
                areas[i][j] = (diff - Math.sin(diff)) / 2;
            }
        }

        double result = Double.POSITIVE_INFINITY;
        double[] dp = new double[n];

        for (int start = 0; start + p <= n; ++start) {
            double forStart = solveGivenStart(areas, c, p, start, dp);
            result = Math.min(result, forStart);
        }
        return result;
    }

    public static void main(String[] args) throws IOException {
        try (BufferedReader in = new BufferedReader(new InputStreamReader(System.in))) {
            int n = Integer.parseInt(in.readLine());
            int p = Integer.parseInt(in.readLine());
            double[] c = new double[n];
            StringTokenizer positions = new StringTokenizer(in.readLine());
            for (int i = 0; i < n; ++i) {
                c[i] = Math.toRadians(Double.parseDouble(positions.nextToken()));
            }
            System.out.println(1e6 * (Math.PI - solve(c, p)));
        }
    }
}