7-11 分段计算居民水费

```

import java.util.Scanner;
public class Main{
    public static void main(String[] args){
        Scanner sc=new Scanner(System.in);
        double a=sc.nextDouble();
        if(a>15){
            System.out.print(String.format("%.2f",2.5*a-17.5));
        }else{
            System.out.print(String.format("%.2f",4*a/3));
        }
    }
}