kipriyanovichAlright, future engineers!
**Pigeonhole Principle:** If you put more items (pigeons) than containers (holes), at least one container must have >1 item. Ex: 3 socks in 2 color categories means 2 socks of the same color! Pro-Tip: It's a simple idea, powerful for proofs! Clearly define your 'pigeons' & 'holes'.