#include<cstdio>

#include<cstring>

#include<cstdlib>

#include<cctype>

#include<cmath>

#include<iostream>

#include<sstream>

#include<iterator>

#include<algorithm>

#include<string>

#include<vector>

#include<set>

#include<map>

#include<stack>

#include<deque>

#include<queue>

#include<list>

#define lowbit(x) (x & (-x))

const double eps = 1e-8;

inline int dcmp(double a, double b){

    if(fabs(a - b) < eps) return 0;

    return a > b ? 1 : -1;

}

typedef long long LL;

typedef unsigned long long ULL;

const int INT_INF = 0x3f3f3f3f;

const int INT_M_INF = 0x7f7f7f7f;

const LL LL_INF = 0x3f3f3f3f3f3f3f3f;

const LL LL_M_INF = 0x7f7f7f7f7f7f7f7f;

const int dr[] = {0, 0, -1, 1, -1, -1, 1, 1};

const int dc[] = {-1, 1, 0, 0, -1, 1, -1, 1};

const int MOD = 1e9 + 7;

const double pi = acos(-1.0);

const int MAXN = 500 + 10;

const int MAXT = 10000 + 10;

using namespace std;

int N;

double R;

double Sin[MAXN][MAXN];

double dist[MAXN][MAXN];

struct Node{

    double x, y, rad;

    void read(){

        scanf("%lf", &rad);

        rad = rad / 180.0 * pi;

        x = R * cos(rad);

        y = R * sin(rad);

    }

}num[MAXN];

double getDist(int i, int j){

    return sqrt((num[i].x - num[j].x) * (num[i].x - num[j].x) + (num[i].y - num[j].y) * (num[i].y - num[j].y));

}

int main(){

    while(scanf("%d%lf", &N, &R) == 2){

        if(N == 0 && R == 0) return 0;

        memset(Sin, 0, sizeof Sin);

        memset(dist, 0, sizeof dist);

        for(int i = 0; i < N; ++i){

            num[i].read();

        }

        for(int i = 0; i < N; ++i){

            for(int j = i + 1; j < N; ++j){

                Sin[i][j] = sin(fabs(num[j].rad - num[i].rad) / 2.0);

                dist[i][j] = dist[j][i] = getDist(i, j);

            }

        }

        double sum = 0.0;

        for(int i = 0; i < N; ++i){

            for(int j = i + 1; j < N; ++j){

                for(int k = j + 1; k < N; ++k){

                    sum += dist[i][j] * dist[i][k] * Sin[j][k] / 2;

                }

            }

        }

        double ans = round(sum);

        printf("%.0lf\n", ans);

    }

    return 0;

}