Acronym Generator

Create an acronym from the first letter of every word, in uppercase. Spaces and hyphens separate words. Remove every other punctuation mark and digit without adding a separator; an apostrophe inside a word does not start another word. Ignore empty pieces.

Implement acronym_generator(phrase).

Input

phrase: The phrase to shorten.

Output

Return the uppercase initials in their original order.

제약 조건

0 ≤ phrase length ≤ 10,000. Input contains ASCII letters, digits, spaces, and punctuation; no tabs or line breaks. A phrase with no letters returns empty text.

예시

입력:
phrase = "central-processing unit"

예상 출력:
expected = "CPU"

입력:
std::string phrase = "central-processing unit";

예상 출력:
std::string expected = "CPU";

입력:
string phrase = "central-processing unit";

예상 출력:
string expected = "CPU";

입력:
phrase = "don't repeat yourself"

예상 출력:
expected = "DRY"

입력:
std::string phrase = "don't repeat yourself";

예상 출력:
std::string expected = "DRY";

입력:
string phrase = "don't repeat yourself";

예상 출력:
string expected = "DRY";

참고 자료

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• Exercism: Acronym