You just keep multiplying, it's a huge number. Now, if I just want the 365 times the 364 in this case, I have to get rid of all of these numbers back here. So one thing I could do is I could divide this thing by all of these numbers. So 363 times 362 all the way down to 1. So that's the same thing as dividing by 363 factorial. 365 factorial divided by 363 factorial is essentially this, because all of these terms cancel out. So this is equal to 365 factorial over 363 factorial over 365 squared.