Computercraft Obsidian Tower Miner

c = 0
height = 0
repeat
    for a = 1, 5 do
        for b = 1, 5 do
            turtle.dig()
            turtle.forward()
        end
        if (c % 2 == 0) and a ~= 5 then
            turtle.turnRight()
            turtle.dig()
            turtle.forward()
            turtle.turnRight()
            c = c + 1
        else
            turtle.turnLeft()
            turtle.dig()
            turtle.forward()
            turtle.turnLeft()
            c = c + 1
        end
    end
    height = height + 1
    turtle.up()
    turtle.turnRight()
    turtle.turnRight()
until not see
turtle.forward()
for a = 1, height do
    turtle.down()
end