#include <iostream>
#include <algorithm>
#include <math.h>
#include <stdio.h>
using namespace std;

int main(){
	double ang, s, sq, r2, res, M[500];
	int n, r, pts;
	while(cin >> n >> r, n + r != 0){
		for(int i = 0; i < n; i++){
                cin >> M[i];
                M[i] = M[i] * M_PI / 180;
		}
		sort(M, M + n);
		res = M_PI * r * r * n * (n - 1) * (n - 2) / 6;
		r2 = r * r / 2.0;
		sq = M_PI * r * r;
		for(int i = 0; i < n; i++){
			for(int j = i + 1; j < n; j++){
				ang = M[j] - M[i];
				if(ang < M_PI){
                        s = r2 * (ang - sin(ang));
				}else{
					ang = 2 * M_PI - ang;
					s = sq - r2 * (ang - sin(ang));
				}
				pts = n - (j - i + 1);
				res = res - s * pts;
				pts = n - 2 - pts;
				res = res - (sq - s) * pts;
			}
		}
		printf("%.f\n", res);
	}

	return 0;
}