sequence m31 = {"January",0,"March",0,"May",0,"July","August",0,"October",0,"December"}
integer y,m,
        nmonths = 0
string months
sequence res = {},
         none = {}

for y=1900 to 2100 do
    months = ""
    for m=1 to 12 do
        if string(m31[m])
        and day_of_week(y,m,1)=6 then
            if length(months)!=0 then months &= ", " end if
            months &= m31[m]
            nmonths += 1
        end if
    end for
    if length(months)=0 then
        none = append(none,y)
    else
        res = append(res,sprintf("%d : %s\n",{y,months}))
    end if
end for

printf(1,"Found %d months with five full weekends\n",nmonths)
res[6..-6] = {" ...\n"}
puts(1,join(res,""))
printf(1,"Found %d years with no month having 5 weekends:\n",{length(none)})
none[6..-6] = {".."}
?none