. . .

I consider 'survival instinct' as one of the most interesting puzzles I've ever come across. Interesting in the sense that unlike other puzzles I couldn't find a heading when I first heard this one. A simple solution it had, but I couldn't crack it. When I finally read the solution I regretted not having given more time to it.

You may find this one very simple, provided you get a correct heading. Good luck.