constexpr int factorial(int n) {
    return n <= 1 ? 1 : n * factorial(n - 1);
}

constexpr int sum_array(const int* arr, size_t size) {
    int sum = 0;
    for (size_t i = 0; i < size; ++i) {
        sum += arr[i];
    }
    return sum;
}

constexpr std::vector<int> make_sequence(int n) {
    std::vector<int> result;
    for (int i = 0; i < n; ++i) {
        result.push_back(i * i);
    }
    return result;
}

constexpr std::string process_text() {
    std::string result = "Hello, ";
    result += "constexpr world!";
    return result;
}

constexpr auto text = process_text(); // Во время компиляции!