#include <iostream>
#include <cmath>
using namespace std;

int main()
{
	int  n, d = 1;
	int n1;
	double s1 = 1, x;
	cin >> n1 >> x;
	int i=1;
		for (int step = 1; step <= n1; ++step && ++i)
		{
			s1 += ((pow(cos(x), step)) / i);
		}

	s1=cos(90);
	cout << s1;
	system("pause");
	return 0;
}