- Cell.jar and inpattern.txt should be in the same folder- Open Cell.jar : # java -jar Cell.jar- Click InPat button :  https://imgur.com/wWalHHO- Type the letter E in the program area : https://imgur.com/4aefPQn- Click parse :  https://imgur.com/Wr2nIPm- And then click step until the counter == 17 : https://imgur.com/V1cHTKu- Click the outpat button, and check outpat.txt :  1 1 . 1 . . . . 1 1 . 1 1 . . . 1 1 . . . . 1 . 1 1 . . . 1 1 . 1 1 . 1 . 1 1 . 1 1 1 . . 1 1- Replace dots : 11010000110110001100001011000110110101101110011- Convert it to hex and then ascii : 686C61636B73 >> hlacks- flag : nactf{hlacks}