find first of a grammar

#include <iostream>
#include <string>

bool isTerminal(char symbol) {
    return symbol >= 'a' && symbol <= 'z';
}

bool isFirstOfA(const std::string& input) {
    if (input.empty()) {
        return false;
    }

    char firstSymbol = input[0];

    if (isTerminal(firstSymbol) || firstSymbol == 'A') {
        return true;
    }

    return false;
}

int main() {
    std::string input;
    std::cout << "Enter a string: ";
    std::cin >> input;

    if (isFirstOfA(input)) {
        std::cout << "The string is in the first of A grammar." << std::endl;
    } else {
        std::cout << "The string is not in the first of A grammar." << std::endl;
    }

    return 0;
}