#include<iostream> using namespace std; int main() { float x; if(0<=x<5){ cout<<fixed<<setprecision(3)<x+2.5; } if(5<=x<10){ cout<<fixed<<setprecision(3)<2-1.5*(x-3)*(x-3); } if(10<=x<20){ cout<<fixed<<setprecision(3)<x/2-1.5; } }