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CF2069A.Was there an Array?
Was there an Array?
For an array of integers , we define its equality characteristic as the array , where if the -th element of the array is equal to both of its neighbors, and if the -th element of the array is not equal to at least one of its neighbors.
For example, for the array , the equality characteristic will be .
You are given the array . Your task is to determine whether there exists such an array for which the given array is the equality characteristic.
Input
The first line contains one integer () — the number of test cases.
Each test case consists of two lines:
- the first line contains one integer ();
- the second line contains integers ().
Output
For each test case, output YES if the array exists, or NO if such an array does not exist. Each letter can be printed in any case.
Note
In the first example, the array is suitable.
In the second example, the array is suitable.
Samples
3
10
0 1 0 0 0 0 1 1
3
1
10
0 1 0 1 1 0 0 1
YES
YES
NO
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