This is a simple string manipulation problem. All you need to do is read the given string $s$, which has length $1 \leq \abs{s} \leq 100$, and convert $s$ to either uppercase or lowercase, preferring that which requires fewer character changes. If there are equal counts of uppercase and lowercase characters in $s$, default to lowercase.
I like using std::transform for stuff like this, since there is very little that can go wrong. Whenever possible, leverage the STL as much as possible!
Keep in mind that strings are immutable in Python, if you prefer that instead.