A. Alex and a Rhombus

Quiz

https://codeforces.com/contest/1180/problem/A

AC Code

https://codeforces.com/contest/1180/submission/55876143

解法

• 数列は1, 5, 13, 25, ...
• OEISに聞く
  • https://oeis.org/search?q=1%2C+5%2C+13%2C+25&language=english&go=Search

計算量

• O(1)