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Problems > Additive Sequence

Additive Sequence

Difficulty: 1000 2000 ms 128 MB

math implementation

Is the sequence additive — every term (from the third) the sum of the two before it?

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

Output: YES or NO (length ≤ 2 is trivially YES).

Constraints:

  • 1 ≤ N ≤ 1000
  • the values fit in 64 bits

Sample Tests

Input 1
5
1 2 3 5 8
Output 1
YES
Input 2
3
1 2 4
Output 2
NO

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