function Mf()
    while turtle.detect() or turtle.detectUp() do
        turtle.dig()
        turtle.digUp()
    end
    while turtle.forward() == false do
    end
end

function Mfnum(num)
    for x=0,num,1 do
        Mf()
    end
end

function Coal()
    if turtle.getFuelLevel() < 40 and turtle.getItemCount(1) < 1 then
        print "Please but some coal in slot 1"
    end
end

function Refuel()
    if turtle.getFuelLevel() < 80 then
        turtle.refuel()
    end
end

function Spiral(num)
    while num>3 do
        Coal()
        Refuel()
        Mfnum(num)
        turtle.turnRight()
        Mfnum(num)
        turtle.turnRight()
        Mfnum(num)
        turtle.turnRight()
        num = num - 3
    end
end

write("Length?")
len=tonumber(read())
Spiral(len)