Me and my girlfriend would like to go to Cuba from Denmark. We would like to go to Miami for a few days before going to Cuba and then spend the rest of the vacation in Cuba. So our flights are as follows:  Denmark-Miami  Miami-Havana  Havana-Denmark  My question is, if this is legal? I have read something about new regulation and that you can not go to Cuba from the USA as a tourist. But it is not easy to figure out, so du any of you know the answer to this?
I may be visiting the US soon for both work (conference) and leisure (sight-seeing) but was wondering whether it is possible to pay a visit to Cuba, as I see that direct commercial flights have been restarted. From what I can tell, it is still not permitted for US citizens to travel to Cuba as tourists (from the ).  What is the legal status of European citizens - would it be permitted for me to travel as a tourist from, say, Florida to Cuba on a commercial flight? Would this cause problems for me on my return to the US?  I understand that the question has been asked before () but the situation has changed and I believe it warrants asking again.
Let $g_n= {2^2}^n +1 $. Prove $g_0 · g_1 · · · g_{n−1} = g_{n} − 2$ Let $g_n= {2^2}^n +1 $. Prove $g_0 · g_1 · · · g_{n−1} = g_{n} − 2$.    I'm not sure how to start this proof, if it should be done algebraically or if I should try to use a proof by induction. Can a person residing in Singapore on a 5-month Employment Pass apply for a Schengen visa? What happens when you target a "magical effect" with Dispel Magic? Can Conjure Animals beasts be used as mounts? Is it possible to use the animals that are summoned using Conjure Animals as mounts?  As an example: Summoning Giant Eagles to carry a group up the mountain or over a wall. Can prematurely powering down a computer cause bad sectors in a hard drive? How can I download an entire website? I'm looking for the fastest way to determine if a long value is a perfect square (i.e. its square root is another integer):    I've done it the easy way, by using the built-in  function, but I'm wondering if there is a way to do it faster by restricting yourself to integer-only domain. Maintaining a lookup table is impractical (since there are about 231.5 integers whose square is less than 263).   Here is the very simple and straightforward way I'm doing it now:  public final static boolean isPerfectSquare(long n) {   if (n &lt; 0)     return false;    long tst = (long)(Math.sqrt(n) + 0.5);   return tst*tst == n; }   Note: I'm using this function in many  problems.  So no one else will ever have to maintain this code.  And this kind of micro-optimization could actually make a difference, since part of the challenge is to do every algorithm in less than a minute, and this function will need to be called millions of times in some problems.    I've tried the different solutions to the problem:   After exhaustive testing, I found that adding 0.5 to the result of Math.sqrt() is not necessary, at least not on my machine. The  was faster, but it gave incorrect results for n >= 410881.  However, as suggested by , we can use the FISR hack for n &lt; 410881. Newton's method was a good bit slower than Math.sqrt().  This is probably because Math.sqrt() uses something similar to Newton's Method, but implemented in the hardware so it's much faster than in Java.  Also, Newton's Method still required use of doubles. A modified Newton's method, which used a few tricks so that only integer math was involved, required some hacks to avoid overflow (I want this function to work with all positive 64-bit signed integers), and it was still slower than Math.sqrt(). Binary chop was even slower.  This makes sense because the binary chop will on average require 16 passes to find the square root of a 64-bit number. According to John's tests, using or statements is faster in C++ than using a switch, but in Java and C# there appears to be no difference between or and switch. I also tried making a lookup table (as a private static array of 64 boolean values).  Then instead of either switch or or statement, I would just say if(lookup[(int)(n&amp;0x3F)]) { test } else return false;.  To my surprise, this was (just slightly) slower. This is because . How do I gunzip all files recursively in a target directory? I'd like to know what is the command to use to gunzip all files in a target directory recursively? I tried to use the unzip command but it didn't work.  I tried the command from I have two tables A &amp; B. Table A id | name | num  Table B id | date | roll  id in table B is a foreign key which relates to the id in table A. I want to get the contents of table B where id is given and also along with that data, I need the name whose id is given from table A. NOTE: cannot use multiple queries separated by commas; need to do both the SELECTs in one query. "a while" vs "awhile" Is there a difference between "awhile" and "a while"? If there is, what is it? I've been wondering this for awhile, but now I actually need the answer. What are the differences between normal and classic difficulties? I can't seem to find a good list of info of all the changes that classic mode offers over normal other than that 'its much harder'.  Does any of the enemy AI improve in classic mode?  Do enemies have more health and do more damage?  Does the panic meter increase faster for countries? I worked, I've worked, I have been working. I need some clarifications Could you help me with these sentences:   I lied to her. (I'm just making a statment)  I've lied to her because the truth would have hurted her.   Second example:   I have been working at Google for 10years. (Meaning I am still working there) I've worked at Google and it was nice.(I don't work anymore) I worked at Google. (Not sure about the difference with the previous one)   I'm learning the different tenses and it isn't so easy for me. Any help would be welcome.  Regards, Same as title, want to kill alt-tab, etc. Encouraging people to explain downvotes Note: If you're looking for a simple explanation as to why comments aren't required on downvotes, see .   I used to get "upset" (though that is too strong a term) when I got downvoted without comment. If my answer isn't good enough then I'd like to know why. Not only does it improve the answer for the OP but it improves my knowledge too.  Where the down-vote has been explained I've found it useful &amp; it has improved my answer, or forced me to delete the answer if it was totally wrong.  So is there any way we can encourage people to leave a comment? Perhaps they don't lose rep if they explain their down-vote?  I must admit though that I haven't always explained my down-vote either so you could call me a hypocrite. I've also grown a thicker skin over the months of using SO (it seems to have come with the higher rep score ;-)), so I'm less bothered about this now. How to nest code within a list using Markdown What is the best way to draw figures with canvas and set their angle? Get most common value for each value of another column in SQL I have a table like this:   Column  | Type | Modifiers  ---------+------+-----------  country | text |   food_id | int  |   eaten   | date |    And for each country, I want to get the food that is eaten most often.  The best I can think of (I'm using postgres) is:  CREATE TEMP TABLE counts AS     SELECT country, food_id, count(*) as count FROM munch GROUP BY country, food_id;  CREATE TEMP TABLE max_counts AS     SELECT country, max(count) as max_count FROM counts GROUP BY country;  SELECT country, max(food_id) FROM counts     WHERE (country, count) IN (SELECT * from max_counts) GROUP BY country;   In that last statement, the GROUP BY and max() are needed to break ties, where two different foods have the same count.  This seems like a lot of work for something conceptually simple.  Is there a more straight forward way to do it? How do I evaluate this integral $\int_0^\pi{\frac{{{x^2}}}{{\sqrt 5-2\cos x}}}\operatorname d\!x$? Show that $$\int\limits_0^\pi{\frac{{{x^2}}}{{\sqrt 5-2\cos x}}}\operatorname d\!x =\frac{{{\pi^3}}}{{15}}+2\pi \ln^2 \left({\frac{{1+\sqrt 5 }}{2}}\right).$$   I don't have any idea how to start, but . centos: using epel repository on a server machine Are there any downsides in enabling epel repository on a server machine or is it something every sysadmin does? What part of speech is there in the sentence “There is a book on the table?”  Also, while typing it out, another question pops up vis-à-vis punctuation. In my complete first sentence above, I ended it with a question mark since my main sentence is a question. The quote is not a question, but it looks like it because of the question mark. Is this the right way to punctuate?