JAVA basic programming exercises-20

Problem: There is a sequence of scores: 2/1, 3/2, 5/3, 8/5, 13/8, 21/13... Find the sum of the first 20 items of this sequence.

public class example1 {
	public static void main(String[] args) {
		double n=2;
		double m=1;
		double sum=0.0;
		for(int i=0;i<20;i++) {
			sum+=n/m;
			double temp=n;
			n=n+m;
			m=temp;
		}
		System.out.println(sum);
	}
}