public class Example3_6 {
    public static void main(String args[]) {
        double sum = 0,item = 1;
        int i = 1,n = 20;
        while(i<n) {
            sum = sum+item;
            i = i+1;
            item = item*(1.0/i);
        }
        System.out.println("sum="+sum);
    }
}