#include<iostream> #include<iomanip> using namespace std; int main() { double n,n1,n2,n3; cin>>n; if(n>=0&&n<=20) { n3=n-10; n2=n-5; n1=n; n=0; if(n3>=0) n+=n3/2-1.5; if(n2>=0) n+=2-1.5*(n2-3)*2; n+=-n1+2.5; cout<<fixed<<setprecision(3)<<n; } return 0; }