Counting the Lines You Skip

A shop prints the same 4-line header at the top of every receipt. Today it prints 6 receipts.

• Without a function: you write all 4 header lines out again for every receipt.
• With a function: you write the 4 header lines once, then add one call line per receipt.

How many fewer lines do you write with the function? (Only count header lines and call lines.)

Enter a whole number.