check if any of the points are same
bool same = true ; same = same & similar ( p1 , p2 ) ; same = same & similar ( p1 , p3 ) ; same = same & similar ( p1 , p4 ) ; same = same & similar ( p2 , p3 ) ; same = same & similar ( p2 , p4 ) ; same = same & similar ( p3 , p4 ) ;