local SLOT_COUNT = 16
function getCoal()
    for slot = 1, SLOT_COUNT, 1 do
        local item = turtle.getItemDetail(slot)
        if(item ~= nil) then
            if(item["name"] == "minecraft:coal") then
                return slot
            end
        end
    end
    return nil
end


while(true) do
    local slot = getCoal()
    turtle.select(slot)
    turtle.dropDown(8)
    sleep(40)

end