/*
 * Copyright Derek Park 2001
 * All rights reserved
 */
import java.awt.Graphics;
import javax.swing.*;

public class pi{    // a class to compute pi

   public static void main(String Args []){   // main method

      // get user input, send to pi(), display results
      JOptionPane.showMessageDialog(null, "PI = " + new Double( pi( Long.parseLong( JOptionPane.showInputDialog( "How many iterations?" ) ) ) ) );
      
      System.exit(0);
      
   }//end main
   
   static double pi(long numOfIterations){  // get input
      double returnVal = 0.0;       // stores return value of pi
      double denominator = 1.0;     // stores current denominator
      int sign = 1;                // stores current sign
      
      for(int i = 0; i <= numOfIterations; i++){   // until it meets the user input
         returnVal += 4.0/denominator*sign;     // add the next term in the series
         denominator += 2;                      // set the denominator up for the next iteration
         sign *= -1;                            // set up the sign for the next iteration
      }
      
      return returnVal; // exit method
      
   }  //end pi
   
}  //end class