package My;

public class Example3_11 
{
	public static void main(String args[])
	{	
        		double r=0, sum=0;
        		int i=1, j=-1;
        		do
        		{	j = j * (-1);
        			r = (double)1/(2*i-1);
            			r = r * j;
            			sum = sum + r;
            			i = i + 1;
        		}
        		while((Math.abs(r)) >=0.00000001);
        		sum*=4;
        		System.out.println("Π的近似值为："+sum);        
	}
}