<p>A sequence of numbers begins with the numbers -1,1,1,...,
and each term afterward is the product of the proceeding three terms.
How many of the first 57 terms of this sequence are negative?</p>
<p>Here from this logic we can see that this is combined of 4 groups.</p>
<p>so 57/4 we removed the remainder and got 14 * 4 = 56;</p>
<p>But now the question is how can I calculate the negatives fast,so if I see this kind of problems in SAT I solve it really fast :).</p>