local function gf(n)
    if n == nil then
        n = 1
    end
    for i = 1, n, 1 do
        while not turtle.forward() do
        end
    end
end

local function gr(n)
    if n == nil then
        n = 1
    end
    for i = 1, n, 1 do
        while not turtle.turnRight() do
        end
    end
end

flag = true
i = 8
while i > 0 do
    turtle.select(1)
    gf(25)
    turtle.digDown()
    turtle.placeDown()
    if flag then
        gr()
    end
    flag = not flag
    i = i - 1
end
gr()
gf(25)
turtle.digDown()
turtle.placeDown()