bool isCorrect(char c) {
    return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || ('а' <= c && c <= 'я') || ('А' <= c && c <= 'Я');
}

string currentWord = "";
char c;
vector<string> words;
while (!in.eof()) {
    in >> c;
    if (!isCorrect(c)) {
        if (currentWord.size() > 0) {
            words.push_back(currentWord);
        }
        currentWord = "";
    } else {
        currentWord += c;
    }
}
if (currentWord.size() > 0) {
    words.push_back(currentWord);
}