# Rounding always favours the protocol, and what mint does against a one-wei reserve

Mentorship Series #14 · 17 December 2025 · [@0xfirefist](https://x.com/0xFireFist) · Mento V3 · Cantina

Mentorship Series · [The Contest Academy](https://0xsimao.com/the-contest-academy) · 0xSimao

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We continued the Mento V3 [contest](https://cantina.xyz/competitions/fe8e03b1-f8db-4698-8a21-44b3a862e434) on Cantina.

**Lesson Summary:**

- Roundings should happen in favour of the protocol, always;
- Can I swap the whole reserve0 or reserve1?
- Let's say totalSupply is 1000, 2000 reserve0 and 1 wei reserve1. If I try to deposit 1000 of each, check mint what will happen;
- Will this take my 1000 token1, given it has no effect on how much liquidity is minted?

https://youtu.be/15RLGhL7Cng

Session video: https://youtu.be/15RLGhL7Cng

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Newer: [Doing the math on the whole rebalancing flow, not just the pool at the end of it](https://0xsimao.com/the-contest-academy/mentorship-series-15) · Older: [Which side of a swap the fee is taken on, and whether it gets taken twice](https://0xsimao.com/the-contest-academy/mentorship-series-13)