Note $$$maxp$$$ as the maximum index of the maximum value in $$$a$$$.

For $$$1 \leq k \leq maxp-1$$$,they do not meet the condition.

For $$$maxp+1 \leq k \leq n$$$,they all meet the condition.

You need to be careful of $$$k==maxp$$$,it meet the condition if and only if there is only one maximum value in $$$a$$$.

Note $$$a_1$$$ as the first $$$\lceil{n/2}\rceil$$$ numbers of $$$a$$$,and $$$a_2$$$ as the last $$$n-\lceil{n/2}\rceil$$$ numbers of $$$a$$$.

Through observation,we found that the following processes will be repeated cyclically:

• erase the leftmost number of $$$a_1$$$

• erase the leftmost number of $$$a_2$$$

• erase the rightmost number of $$$a_1$$$

• erase the rightmost number of $$$a_2$$$

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