import java.util.Scanner;
public class Test2{
public static void main(String[] args){
Scanner sc=new Scanner(System.in);
System.out.println("请输入通话时间（秒）:");
int time=sc.nextInt();
double pay=0.0;
int temp=0;
if(time<=180){
pay=0.2;
}else if(time%60==0){
temp=(time-180)/60;
System.out.println(temp);
pay=0.2+0.1*temp;//为什么
}else{
pay=0.2+0.1*temp+0.1;
}
System.out.println(pay);
}
}