#include<stdio.h> 
int main()
{
	double min,s;
	printf("请输入通话时间\n");
	scanf("%lf",&min);
	if(min<=3)
	{
		s=0.5;		
	}	    
	else
	{
		s=(min-3)*0.15+0.5;    
	}        
    printf("应缴话费为%.1lf\n",s);
}