The amount of weight that Lily can lift grows linearly. This means that we can develop a linear equation of how much she is able to lift in the form of:

Where $B$ is how much more she can lift every week, and $A$ is how much she can lift at the start.

The only trick to this problem is to note that we don’t add $B$ to the amount she can lift $N$ times, as Lily’s doesn’t get stronger until the second week. So, we have $x = N - 1$.

The final output for each test case is $B \times (N - 1) + A$.

Time complexity

$\mathcal{O}(1)$

Problem

Read the problem.