HackerRank Problem: Code works on VS Code but not on the HackerRank site

[Pnerd]

Hi, I'm trying to solve this HackerRank problem: https://www.hackerrank.com/challenges/py...dd/problem

This is my code:

countries = set()
n = int(input())
for i in range(n):
    countries.add(input())
print(len(countries))

It works when I run it on VS Code, but gives the following error when I try to run the code on the HackerRank site:

Error:
Traceback (most recent call last):
  File "Solution.py", line 5, in <module>
    countries.add(input())
  File "<string>", line 1, in <module>
NameError: name 'UK' is not defined

What am I doing wrong here?
.