#include<iostream> #include<iomanip> using namespace std; int main() { double x,y; cin>>x; if(0<=x&&x<5){ y=-x+2.5; cout<<fixed<<setprecision(3)<<y<<endl; } else if(5<=x&&x<10){ y=2-1.5*(x-3)*2; cout<<fixed<<setprecision(3)<<y<<endl; } else{ y=x/2-1.5; cout<<fixed<<setprecision(3)<<y<<endl; } return 0; }