local args = {...}
if #args ~= 1 then
    print("Usage: big_tunnel <length>")
    return
end

function dig(direction)
    if direction == "forward" then
        while turtle.detect() do turtle.dig() end
    elseif direction == "up" then
        while turtle.detectUp() do turtle.digUp() end
    elseif direction == "down" then
        while turtle.detectDown() do turtle.digDown() end
    end
end

turtle.up()
local right = true
for i=1,args[1] do
    dig("forward")
    turtle.forward()
    dig("up")
    dig("down")
    if right then
        turtle.turnRight()
        right = false
    else
        turtle.turnLeft()
        right = true
    end
    for j=1,5 do
        dig("forward")
        turtle.forward()
        dig("up")
        dig("down")
    end
    if right then
        turtle.turnRight()
    else
        turtle.turnLeft()
    end
end

turtle.turnRight()
turtle.turnRight()
turtle.up()
dig("up")
turtle.up()
dig("up")
turtle.up()
dig("up")
if right then
    right = false
else
    right = true
end
for i=1,args[1] do
    if(i ~= 1) then
        dig("forward")
        turtle.forward()
        dig("up")
        dig("down")
    end
    if right then
        turtle.turnRight()
        right = false
    else
        turtle.turnLeft()
        right = true
    end
    for j=1,5 do
        dig("forward")
        turtle.forward()
        dig("up")
        dig("down")
    end
    if right then
        turtle.turnRight()
    else
        turtle.turnLeft()
    end
end

turtle.turnRight()
turtle.turnRight()
turtle.up()
dig("up")
if right then
    right = false
else
    right = true
end
for i=1,args[1] do
    if(i ~= 1) then
        dig("forward")
        turtle.forward()
        dig("up")
        dig("down")
    end
    if right then
        turtle.turnRight()
        right = false
    else
        turtle.turnLeft()
        right = true
    end
    for j=1,5 do
        dig("forward")
        turtle.forward()
        dig("up")
        dig("down")
    end
    if right then
        turtle.turnRight()
    else
        turtle.turnLeft()
    end
end