#include<stdio.h>
void main()
{
	printf("˰ǰ\n");
	int qian;
	scanf("%d",&qian);
	if(qian<=3500)
	{
		printf("˰:0");
	}
	else if(qian>3500&&qian<8000)
	{
		int a=(qian-3500)*0.02;
		printf("˰:%d",a);
	}
	else if(qian>8000&&qian<20000)
	{
		int a=(qian-3500)*0.02+(qian-8000)*0.05;
	    printf("˰:%d",a);	
	}
	else if(qian>20000)
	{
		int a=(qian-3500)*0.02+(qian-8000)*0.05+(qian-20000)*0.1;
		printf("˰:%d",a);
	}
}