Wikipedia
The McNuggets version of the coin problem was introduced by Henri Picciotto,
who included it in his algebra textbook co-authored with Anita Wah. Picciotto
thought of the application in the 1980s while dining with his son at
McDonald's, working the problem out on a napkin. A McNugget number is
the total number of McDonald's Chicken McNuggets in any number of boxes.
In the United Kingdom, the original boxes (prior to the introduction of
the Happy Meal-sized nugget boxes) were of 6, 9, and 20 nuggets.

Task

Calculate (from 0 up to a limit of 100) the largest non-McNuggets
number (a number n which cannot be expressed with 6x + 9y + 20z = n
where x, y and z are natural numbers).




const Limit = 100
 
var mcnuggets: array[0..Limit, bool]
 
for a in countup(0, Limit, 6):
  for b in countup(a, Limit, 9):
    for c in countup(b, Limit, 20):
      mcnuggets[c] = true
 
for n in countdown(Limit, 0):
  if not mcnuggets[n]:
    echo "The largest non-McNuggets number is: ", n
    break