Arithmetic or Not

Difficulty: 900 3000 ms 128 MB

math

Is the sequence an arithmetic progression (constant difference between consecutive terms)?

Input: the first line has N; the second line has N integers.

Output: YES or NO.

Constraints:

• 1 ≤ N ≤ 10⁵
• |a_i| ≤ 10⁹

Sample Tests

4
5 8 11 14

YES

3
1 2 4

NO

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