#include <stdio.h>
 #include <math.h>
int main()
{
int x;
double b;
double GPA;
 x=(x>=0&&x<=100);
scanf("%d",&x);
if(x>=90&&x<=100){
printf("4.0\n");
}
if(x>=60&&x<=89){
GPA=4-0.1*(90-x);
printf("%.1lf\n",GPA);
}
if(x>36&&x<60){
 b=sqrt(x)*10;
 double c=floor(b);
 GPA=4-0.1*(90-c);
 printf("%.1lf",GPA);}
 if(x>=0&&x<=36){
     printf("0.0");}

return 0;
}