please adapt this c64 chatbot in C for cc65: #include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include <iostream>
#include <fstream>
#include <vector>
#include <string>

std::vector<std::string> responses;

void load_responses(const std::string& filename) {
    std::ifstream file(filename);
    std::string line;
    while (std::getline(file, line)) {
        responses.push_back(line);
    }
}

int main() {
    load_responses("responses.txt");

    char input[80];
    printf("Chatbot: Hello! How can I help you?\n");

    while (1) {
        printf("User: ");

        fgets(input, sizeof(input), stdin);
        input[strcspn(input, "\n")] = '\0';
        for (int i = 0; i < strlen(input); i++) {
            input[i] = tolower(input[i]);
        }

        size_t response_index = 0;
        for (response_index = 0; response_index < responses.size(); response_index++) {
            if (responses[response_index] == input) {
                break;
            }
        }

        if (response_index == responses.size()) {
            printf("Chatbot: Sorry, I don't understand.\n");
        } else {
            std::cout << responses[response_index] << "\n";
            response_index++;
            while (response_index < responses.size()) {
                std::cout << responses[response_index] << "\n";
                response_index++;
            }
        }
    }

    return 0;
}