Problem:
Score : 1000 points

Problem Statement

Given are N points on the circumference of a circle centered at (0,0) in an xy-plane.
The coordinates of the i-th point are (\cos(\frac{2\pi T_i}{L}),\sin(\frac{2\pi T_i}{L})).

Three distinct points will be chosen uniformly at random from these N points.
Find the expected x- and y-coordinates of the center of the circle inscribed in the triangle formed by the chosen points.

Constraints

3 \leq N \leq 3000

N \leq L \leq 10^9

0 \leq T_i \leq L-1

T_i<T_{i+1}

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N L
T_1
:
T_N

Output

Print the expected x- and y-coordinates of the center of the circle inscribed in the triangle formed by the chosen points.
Your output will be considered correct when the absolute or relative error is at most 10^{-9}.

Sample Input 1

3 4
0
1
3

Sample Output 1

0.414213562373095 -0.000000000000000

The three points have the coordinates (1,0), (0,1), and (0,-1). The center of the circle inscribed in the triangle formed by these points is (\sqrt{2}-1,0).

Sample Input 2

4 8
1
3
5
6

Sample Output 2

-0.229401949926902 -0.153281482438188

Sample Input 3

10 100
2
11
35
42
54
69
89
91
93
99

Sample Output 3

0.352886583546338 -0.109065017701873

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        FastScanner in = new FastScanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        D_Incenters solver = new D_Incenters();
        solver.solve(1, in, out);
        out.close();
    }

    static class D_Incenters {
        public void solve(int testNumber, FastScanner in, PrintWriter out) {
            int n = in.nextInt();
            int L = in.nextInt();
            double[] t = new double[n];
            for (int i = 0; i < n; i++) {
                t[i] = in.nextDouble();
            }

            double U = 2 * Math.PI / L;
            double[] cosTable = new double[n];
            double[] sinTable = new double[n];
            for (int i = 0; i < n; i++) {
                cosTable[i] = Math.cos(U * 0.5 * t[i]);
                sinTable[i] = Math.sin(U * 0.5 * t[i]);
            }

            double x = 0;
            double y = 0;
            for (int i = 0; i < n; i++) {
                for (int j = i + 1; j < n; j++) {
                    outer:
                    for (int si = -1; si <= 1; si += 2) {
                        for (int sj = -1; sj <= 1; sj += 2) {
                            double xu = si * cosTable[i];
                            double yu = si * sinTable[i];
                            double xv = sj * cosTable[j];
                            double yv = sj * sinTable[j];

                            double xp = xu * xv - yu * yv;
                            double yp = xu * yv + xv * yu;
                            xp = -xp;
                            yp = -yp;

                            if (cross(xu, yu, xp, yp) > 0 && cross(xp, yp, xv, yv) > 0) {
                                int am = j - i - 1;
                                x -= xp * am;
                                x += xp * (n - 2 - am);
                                y -= yp * am;
                                y += yp * (n - 2 - am);
                                break outer;
                            }
                        }
                    }

                }
            }
            x /= (double) n * (n - 1) * (n - 2) / 6.0;
            y /= (double) n * (n - 1) * (n - 2) / 6.0;
            out.printf("%.15f %.15f", x, y);
        }

        private double cross(double x1, double y1, double x2, double y2) {
            return x1 * y2 - x2 * y1;
        }

    }

    static class FastScanner {
        private BufferedReader in;
        private StringTokenizer st;

        public FastScanner(InputStream stream) {
            in = new BufferedReader(new InputStreamReader(stream));
        }

        public String next() {
            while (st == null || !st.hasMoreTokens()) {
                try {
                    st = new StringTokenizer(in.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return st.nextToken();
        }

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

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

    }
}