So you learned binary search in your algorithms class and now you think you can apply it to real life? Cool, cool. Just remember that in the real world, guessing someone's age by saying "50" and then "25" is basically telling them they look 50 first. Congratulations, you just optimized your way into sleeping on the couch with O(log n) efficiency. Pro tip: some problems are better solved with linear search, even if it's slower. Like maybe start at 21 and work your way up slowly? Your relationship will thank you for the extra time complexity.