[Community Question] Geometry: Exercise about trivial fundamental group.

One of our user asked:

I everybody, I have to solve this exercise. I have to find two topological spaces $Y_1$, $Y_2$ such that $\pi (Y_1)=\pi (Y_2)= (0)$ but $\pi (Y_1 \cup Y_2)\ne (0)$. Can you help me?