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

int main() {
    FILE *input = fopen("input.txt", "r");
    if (input == NULL) {
        perror("Cannot open the input file");
        return 1;
    }

    FILE *output = fopen("output.txt", "w");
    if (output == NULL) {
        perror("Cannot create the output file");
        fclose(input);
        return 1;
    }

    char line[1000];
    char previousLines[1000][1000];
    int numLines = 0;

    while (fgets(line, sizeof(line), input)) {
        int isDuplicate = 0;

        // Check if the current line is a duplicate
        for (int i = 0; i < numLines; i++) {
            if (strcmp(line, previousLines[i]) == 0) {
                isDuplicate = 1;
                break;
            }
        }

        if (!isDuplicate) {
            strcpy(previousLines[numLines], line);
            numLines++;
            fputs(line, output);
        }
    }

    fclose(input);
    fclose(output);

    printf("Unique lines extracted successfully into 'output.txt'\n");

    return 0;
}