#include <iostream>
#include<cmath>
#include <iomanip>

using namespace std;

int main() {
	double x, y, angle;
	cin >> x >> y;
	if (x == 0 && y > 0) {
		angle = 3.1415926535 / 2;
		cout << fixed << setprecision(5) << angle;
		return 0;
	}
	if (x == 0 && y < 0) {
		angle = 3.1415926535 / (-2);
		cout << fixed << setprecision(5) << angle;
		return 0;
	}
	if (x == 0 && y == 0) {
		cout << 0;
		return 0;
	}
	double tg = y / x;
	//cout << "tg = " << tg << endl;
	double cos = sqrt(1 / (1 + (tg * tg)));
	//cout << "cos = " << cos << endl;
	angle = acos(cos);
	//cout << fixed << setprecision(5) << angle;

	if (x >= 0 && y >= 0)
	{
		cout << fixed << setprecision(5) << angle;
		return 0;
	}
	if (x <= 0 && y >= 0)
	{
		angle = 3.1415926535 - angle;
		cout << fixed << setprecision(5) << angle;
		return 0;
	}
	if (x >= 0 && y <= 0)
	{
		angle = angle * (-1);
		cout << fixed << setprecision(5) << angle;
		return 0;
	}
	angle = -3.1415926535 + angle;
	cout << fixed << setprecision(5) << angle;
	return 0;
}