#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <stdio.h>
#include <fstream>
#include <cmath>
#include <iomanip>

using namespace std;

int main()
{
    long double x, y;
    ifstream file_in("angle1.in");
    file_in >> x >> y;
    file_in.close();

    long double ang = 0;
    ang = atan2(y, x);

    ofstream file_out("angle1.out");
    file_out << setprecision(15) << ang;
    file_out.close();

    //system("pause");
    return 0;
}