function p(y as unsigned integer) as unsigned integer
    return ( y + int(y/4) - int(y/100) + int(y/400) ) mod 7
end function

function islongyear( y as uinteger ) as boolean
    if p(y) = 4 then return true
    if p(y-1) = 3 then return true
    return false
end function

print islongyear(1998)
print islongyear(2020)
print islongyear(2021)