#include <stdio.h>
#include <stdlib.h>

int is_word_starting_with_a(char first_char) {
    return (first_char == 'a' || first_char == 'A');
}

void filterWordsStartingWithA(FILE *input_file, FILE *output_file) {
    char *line = NULL;
    size_t len = 0;
    ssize_t read;
    int inside_word = 0;

    while ((read = getline(&line, &len, input_file)) != -1) {
        for (int i = 0; line[i] != '\0'; i++) {
            if (line[i] == ' ' || line[i] == '\t' || line[i] == '\n') {
                // End of word, reset state
                inside_word = 0;
            } else {
                // Start of a new word
                if (!inside_word) {
                    inside_word = 1;
                    // Check if the word starts with 'a'
                    if (is_word_starting_with_a(line[i])) {
                        fprintf(output_file, "%c", line[i]);
                    }
                } else {
                    // Inside a word, continue writing characters
                    fprintf(output_file, "%c", line[i]);
                }
            }
        }

        fprintf(output_file, "\n");
    }

    free(line);
}

int main() {
    char input_file_path[] = "data.txt";
    char output_file_path[] = "result.txt";

    FILE *input_file = fopen(input_file_path, "r");
    FILE *output_file = fopen(output_file_path, "w");

    if (input_file == NULL || output_file == NULL) {
        perror("Error opening files");
        return 1;
    }

    filterWordsStartingWithA(input_file, output_file);

    fclose(input_file);
    fclose(output_file);

    return 0;
}