I have been asked something similar about 7 years ago, when I went to renew my Green Card, few days ahead of my scheduled appearance. The agent, a math major w

I have been asked something similar about 7 years ago, when I went to renew my Green Card, few days ahead of my scheduled appearance. The agent, a math major with a sense of humor, asked me to do 12 factorial and then he woulde accommodate me. I did, and he held his side. But I kindly doubt this guy's binary search claim.