Morris' Blog 我在摸索我存在的意義、生命的意義、內涵及價值。 沒有真正神手般的厲害，套用模式是大部分的情況。 沒那麼厲害的我存在的意義為何，襯托出神的存在？ 有時候不能怪別人不給我機會，我已經開始省思， 為什麼我沒有給別人機會的原因，而是全要靠別人。 有時候我認為我與眾不同，那是因為我做不到很多人能辦到的事情。 我聽不到、玩不起來、說得不夠明瞭、理解得不夠多， 我缺少的語文能力，就是一切一切無能的判定。 為此，我不曉得能做些對別人有幫助的事情。 我知道我自己是個不服輸的性格，但現在我不得不認輸。 我沒有能力，因此我必須認輸。 我到底來這世界作什麼？處處充滿不確定性， 而我總是無法出類拔萃，想當個一般人似乎也回不了頭了。 越強大的挑戰需要越強力的支持，而我的支持是什麼？ 最近嘗試與人談話，但都是失敗的結局，沒人能接受， 不需要言語，不需要溝通，一切所想都表達不出來。

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Problem C
Critical Wave

Input: standard input
Output: standard output
Time Limit: 10 seconds

The task is simple. Through some critical points in 2D, you are to draw a wave like curve. Your goal is to include as many points as possible.

• There will be an imaginary line y = a, which we call the major axis for the curve.
• All the points on the curve should have different x coordinates. Their y coordinates should be of form a-1 or a+1.

Two consecutive points on the curve should have a difference of 2 in their y coordinate

Input

There will be no more than 222 test cases. Each test case starts with an integer N, the number of points in the test case. In the next N lines, there will be N pair of integers giving the x and y coordinate of the points. There will be no more than 1000 points in each test case. All coordinates are integers -- they'd fit in an signed 2 byte integer data type.

Output

For each test case print a number -- the maximum number of critical points that can be included in a curve drawn from the given points.

Sample Input

10

0 1

1 0

1 -1

2 -2

3 1

3 -1

3 -2

4 1

4 -1

5 –1

10

0 1

1 0

1 -1

2 -2

3 1

3 -1

3 -2

4 1

4 -1

5 –1

Sample Output

4

4

Problem-setter: Monirul Hasan Tomal

“If you don’t consider your life as a journey you will advance nowhere and life will appear to you as an endless and hopeless track.”