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## C - A x B + C Editorial by evima

For each pair $$(A,B)$$ of positive integers such that $$A \times B \lt N$$, a positive integer $$C$$ such that $$A \times B + C = N$$ is uniquely determined. Therefore, it is sufficient to count the number of such pairs of positive integers $$(A,B)$$.

When $$A$$ is fixed, the number of possible $$B$$ is $$\left \lfloor \cfrac{N - 1}{A} \right \rfloor$$. Therefore, we could solve the problem by performing exhaustive search on $$A$$ from $$1$$ to $$N-1$$.

Sample code in Python: https://atcoder.jp/contests/abc179/submissions/16844575

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