function isfull()
    for i=1,16,1 do
        if turtle.getItemSpace(i) > 0 then
            return false
        end
    end
    return true
end

function dig_three_blocs(upordown)
    if turtle.detect() == true then
        turtle.dig()
    end
    for i=1,2,1 do
        if upordown == false then
            turtle.up()
        end
        if upordown == true then
            turtle.down()
        end
        if turtle.detect() == true then
            turtle.dig()
        end
    end
end


function main()
    local upordown = false
    while isfull() == false do
        if turtle.getFuelLevel() < 3 then
            turtle.select(2)
            turtle.refuel(1)
            turtle.select(1)
        end
        dig_three_blocs(upordown)
        turtle.forward()
        upordown = not upordown
    end
end

main()