Merge pull request atcoder#102 from rsk0315/fix/document

Author: yosupo06

document_en/math.md

@@ -78,7 +78,7 @@ It returns the answer in $\bmod 2^{\mathrm{64}}$, if overflowed.
 
 **@{keyword.complexity}**
 
-- $O(\log{(m+a)})$
+- $O(\log m)$
 
 ## @{keyword.examples}
 

document_ja/math.md

@@ -75,7 +75,7 @@ $$\sum_{i = 0}^{n - 1} \left\lfloor \frac{a \times i + b}{m} \right\rfloor$$
 
 **@{keyword.complexity}**
 
-- $O(\log{(m+a)})$
+- $O(\log m)$
 
 ## @{keyword.examples}