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).




BEGIN
    # Solve the McNuggets problem: find the largest n <= 100 for which there #
    # are no non-negative integers x, y, z such that 6x + 9y + 20z = n       #
    INT max nuggets = 100;
    [ 0 : max nuggets ]BOOL sum;
    FOR i FROM LWB sum TO UPB sum DO sum[ i ] := FALSE OD;
    FOR x FROM 0 BY 6 TO max nuggets DO
        FOR y FROM x BY 9 TO max nuggets DO
            FOR z FROM y BY 20 TO max nuggets DO
                sum[ z ] := TRUE
            OD # z #
        OD # y #
    OD # x # ;
    # show the highest number that cannot be formed                          #
    INT largest := -1;
    FOR i FROM UPB sum BY -1 TO LWB sum WHILE sum[ largest := i ] DO SKIP OD;
    print( ( "The largest non McNugget number is: "
           , whole( largest, 0 )
           , newline
           )
         )
END