// Monte Carlo calculation of Pi 

import java.util.Random;
import java.io.*;

class Pi {

  public static void main (String[] args) throws IOException {

    Random point  = new Random();
    int i,n,inside;
    float x,y;       // Coordinates of a random point 

    BufferedReader stdin;
    stdin = new BufferedReader (new InputStreamReader (System.in));

    System.out.print ("Enter the number of random points: ");
    n = Integer.parseInt (stdin.readLine());

    inside = 0; 
    for (i = 1; i <= n; i++) { 
       x = point.nextFloat()*2-1;    // Generate a random point
       y = point.nextFloat()*2-1;
       if (x*x + y*y <= 1) inside++; // if inside the unit circle increment counter
       }

    System.out.print ("Pi = " + 4*(float)inside/n);
     
    }
}