杭电 2009 ( 求数列的和 ) java

import java.util.Scanner;
import java.text.DecimalFormat;
public class Main {

public static void main(String[] args) {

Scanner sc=new Scanner(System.in);
while(sc.hasNext()){
double n=sc.nextDouble();
int m=sc.nextInt();
int i=1;
double sum=0;

for(int j=0;j<m;j++)
{
sum=sum+n;
n=Math.sqrt(n);

}
DecimalFormat df2=new DecimalFormat("##.00");

System.out.println(df2.format(sum));
}
}

}