#include<stdio.h>
int main(){
int a;
double b;
scanf("%d",&a);
if(a<5000){
b=a*0.2;
printf("%.1f\n",b);}
else if(a>=5000&&a<10000){
b=a*0.3;
printf("%.1f\n",b);}
else(a>=10000){
b=a*0.5;
printf("%.1f\n",b);}
return 0;
}