Bridge

local x = 1

function line()   -- place a line x blocks long
    for i = 1,x do
       turtle.forward()
       turtle.placeDown()
    end
 end

function reverse()        --does a full 180 in the same block
    turtle.turnLeft()
    turtle.turnLeft()
 end

term.write("length = ")  --gets x from the user
x = tonumber(read())

line()
reverse()

for i = 0, (x-2) do
    turtle.forward()
end