#include<iostream> #include<cmath> using namespace std; int main(){ double x,y; cin>>x; if(x>=0 && x<5){ y=-1*x+2.5; } else if(x>=5 && x<10){ y=2-1.5*(x-3)*2; } else{ y=x/2-1.5; } printf("%.3lf",y); return 0; }