//Hero.java
//calculate area of triangle given lengths of its 3 sides

import java.awt.*;
import javax.swing.*;

public class Hero {

    public static void main (String [] args) {

        String input;
        double a, b, c;
        double s;
        double area;
 	
        input = JOptionPane.showInputDialog( "Enter length of side 1" );
        a = Double.parseDouble( input );
        input = JOptionPane.showInputDialog( "Enter length of side 2" );
        b = Double.parseDouble( input );
        input = JOptionPane.showInputDialog( "Enter length of side 3" );
        c = Double.parseDouble( input );

	s = (a+b+c) / 2;   //"semiperimeter"
 	area = Math.sqrt(s*(s-a)*(s-b)*(s-c));  //Hero[n]'s formula
 	
 	JOptionPane.showMessageDialog(null,"Area = " + area);
    }
} 
/* 1 1 1 = .433         equilateral triangle
   1 1 1.41421 = .5     unit square
   1 1.73025 2 = .866   30-60-90 triangle
   1 2 2.23606 = 1      
   3 4 5 = 6            first Pythagorean triple right triangle
*/