We mark point $O_1$ on a unit circle and, using $O_1$ as the center, we mark (by means of a compass) we mark point $O_2$ on the circle (clockwise starting with $O_1$). Using point $O_2$ as a new center, we repeat the procedure in the same direction with the same radius; and so on. After we had marked point $O_{1968}$ a circle is cut through each mark so we get 1968 arcs. How many different arc lengths can we thus procure?

Let's think step by step and output the final answer within \boxed{}.
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