Write a function to return the city from each of these vacation spots.
grabCity("[Last Day!] Beer Festival [Munich]") ➞ "Munich"
grabCity("Cheese Factory Tour [Portland]") ➞ "Portland"
grabCity("[50% Off!][Group Tours Included] 5-Day Trip to Onsen [Kyoto]") ➞ "Kyoto"
There may be additional brackets, but the city will always be in the last bracket pair.