#include <iostream>
#include <CGAL/Simple_cartesian.h>
#include <CGAL/Point_2.h>
#include <CGAL/predicates_on_points_2.h>
typedef CGAL::Simple_cartesian<double> Kernel;
typedef Kernel::Point_2 Point_2;
 
int main()
{
    Point_2 a(1,1), b(3, 3), c(5, 5);
    switch (CGAL::orientation(a, b, c))
    {
        case CGAL::LEFT_TURN:
            std::cout << "Left turn."; break;
        case CGAL::RIGHT_TURN:
            std::cout << "Right turn."; break;
        case CGAL::COLLINEAR:
            std::cout << "The three points lie on a line."; break;
    }
    return 0;
}