Problem - Giant Pizza

Problem: $n$ people are choosing toppings for a pizza. Each person specifies two topping preferences with conditions like "I want topping $x$" or "I don't want topping $y$". Each person must get at least one of their wishes. Can you satisfy everyone?

Link: CSES 1684

Constraints:

• $1 \leq n \leq 10^5$ people
• $1 \leq m \leq 10^5$ toppings

Output: A valid topping selection, or "IMPOSSIBLE".