Varun has to call his friend Amar, but he doesn't remember Amar's phone number. He has two options, first to try calling Amar directly and in case he doesn't get the number right he could try the second option of calling up Vineet, another friend of his who would in turn give cosmic_glitch's number of who finally give him Amar's number. Alternatively, Varun can try the second option first. Given Varun needs to minimize the total number of calls he has to make, what should be the minimum level of certainity that Varun should have regarding the number he already has so that it would be advisable for him to try the first option before the second?