[evgen]

Given the amount of attention that has been paid to just this sort of scenario for more than two decades (along with prodigious spending on detection capability at ports) I would bet large sums that the answer to that is 0 or possibly 1. The danger of what you suggest is in getting caught, and the terribly unpleasant consequences of same; if I were in charge when some country tried that my first question would be if we knew where every family member of the leadership of that country slept...