Insert all the points in a set
for ( int i = 0 ; i < n ; i ++ ) pts . add ( points . get ( i ) ) ; for ( int i = 0 ; i < n ; i ++ ) for ( int j = i + 1 ; j < n ; j ++ ) { int x = points . get ( i ) . first + points . get ( j ) . first ; int y = points . get ( i ) . second + points . get ( j ) . second ;