#include <stdio.h>

#define MAX_LINE_LENGTH 1000

int is_word_starting_with_a(const char *word) {
    return (word[0] == 'a' || word[0] == 'A');
}

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;
    }

    char line[MAX_LINE_LENGTH];
    char word[MAX_LINE_LENGTH];

    while (fgets(line, sizeof(line), input_file) != NULL) {
        int i = 0;
        int j = 0;

        while (line[i] != '\0') {
            if (line[i] == ' ' || line[i] == '\t' || line[i] == '\n') {
                // End of word, check and write to output if it starts with 'a'
                word[j] = '\0';
                if (is_word_starting_with_a(word)) {
                    fprintf(output_file, "%s ", word);
                }
                // Reset for the next word
                j = 0;
            } else {
                // Copy characters to the current word
                word[j++] = line[i];
            }
            i++;
        }

        // Check and write the last word in the line
        word[j] = '\0';
        if (is_word_starting_with_a(word)) {
            fprintf(output_file, "%s", word);
        }

        fprintf(output_file, "\n");
    }

    fclose(input_file);
    fclose(output_file);

    return 0;
}