For the four circles \( M \), \( N \), \( O \) and \( P \), following four equations are given:
Circle \( M \): \( x^2 + y^2 = 1 \)
Circle \( N \): \( x^2 + y^2 - 2x = 0 \)
Circle \( O \): \( x^2 + y^2 - 2x - 2y + 1 = 0 \)
Circle \( P \): \( x^2 + y^2 - 2y = 0 \)
If the centre of circle \( M \) is joined with centre of the circle \( N \), further centre 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:
