Contribute correction: Sudoku

  _  _      ___     _    _      ___    
 | \| ||   / _ \\  | |  | ||   / _ \\  
 |  ' ||  | / \ || | |/\| ||  | / \ || 
 | .  ||  | \_/ || |  /\  ||  | \_/ || 
 |_|\_||   \___//  |_// \_||   \___//  
 `-` -`    `---`   `-`   `-`   `---`