/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.math.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		double A= -0.5,B=-0.4,C=7, X0=0.3, Y0=0.2;
		double X0Y0= Math.pow(X0-A, 2) + Math.pow(Y0-B, 2) + C*Math.exp(-(Math.pow(X0+A, 2))-Math.pow(Y0+B, 2));
        double X1Y0= Math.pow(X0+0.1-A, 2) + Math.pow(Y0-B, 2) + C*Math.exp(-(Math.pow(X0+0.1+A, 2))-Math.pow(Y0+B, 2));
        double X0Y1= Math.pow(X0-A, 2) + Math.pow(Y0+0.1-B, 2) + C*Math.exp(-(Math.pow(X0+A, 2))-Math.pow(Y0+0.1+B, 2));

        double gx=(X1Y0-X0Y0)/0.1;
        double gy=(X0Y1-X0Y0)/0.1;

        double rez=Math.atan2(gy, gx);
        System.out.println(rez);
        
	}
}