Circle

For the four circles M, N, O and P, following four equations are given : Circle M : x² + y² = 1 Circle N : x² + y² $-$ 2x = 0 Circle O : x² + y² $-$ 2x $-$ 2y + 1 = 0 Circle P : x² + y² $-$ 2y = 0 If the centre of circle M is joined with centre of the circle N, further center of circle N is joined with centre of the circle O, centre of circle O is joined with the centre of circle P and lastly, centre of circle P is joined with centre of circle M, then these lines form the sides of a :