Can anyone please explain me easier way the question (question link given below). I didnt understand the question since my geometry knowledge is very low. Also It would be great if you explain also the solution for the problem actually I didnt solve any problem from geometry.

Sorry for my poor English. Thanks In Advance https://codeforces.com/contest/1096/problem/C

What exactly you can't understand exactly? Which sentence in the problem description?

We can't explain everything, and most of the definitions are available on Wikipedia anyway, see https://en.wikipedia.org/wiki/Regular_polygon for example.

Without losing generality, it can be assumed that a regular polygon

Gwithn≥ 3 vertices is centered at the origin, and that it is circumscribed by a unit circle with radiusR= 1 that passes through all these vertices. Note that G consists ofnidentical isosceles triangles with angles {90 - 180 /n, 90 - 180 /n, 360 /n} degrees and sides {1, 1, 2sin(π /n)}. Vertices ofGcan be enumerated asV= {0, 1, ...,n- 1}, such that vertex is located at polar angle θ_{i}= 360 ×i/n. Let us assume that the tripleT= {a,b,c} is a subset ofVsuch that 0 ≤a<b<c≤n- 1. It can be shown that , wherek=c-aand 2 ≤k≤n- 1. In fact, is an incsrcibed angle whose value depends on the polar angle difference betweencanda, and is independent of the location ofb. The problem is then reduced to the simpler problem of finding the smallestn≥ 3 for the given integer degrees that satisfies the previous equation.The following is a C++14 program that generates all the 22 minimum-size regular polygons that include all inscribed angles . The list next to each polygon is the values of the inscribed angle(s) that such polygon includes.

https://ideone.com/3Eluk8