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C - ABC Tournament /

Time Limit: 2 sec / Memory Limit: 1024 MB

### 問題文

トーナメント表は完全二分木の形をしています。
より正確には、このトーナメントは以下の要領で行われます。

• i = 1, 2, 3, \dots, N について順に、以下のことが行われる。

• 各整数 j (1 \le j \le 2^{N - i}) について、まだ負けたことのない選手のうち、 2j - 1 番目に番号の小さい選手と 2j 番目に番号の小さい選手が対戦する。

### 制約

• 1 \le N \le 16
• 1 \le A_i \le 10^9
• A_i は相異なる
• 入力に含まれる値は全て整数である

### 入力

N
A_1 A_2 A_3 \dots A_{2^N}


### 入力例 1

2
1 4 2 5


### 出力例 1

2


まず選手 12、選手 34 がそれぞれ対戦し、レートの大小から選手 24 が勝利します。

### 入力例 2

2
3 1 5 4


### 出力例 2

1


まず選手 12、選手 34 がそれぞれ対戦し、レートの大小から選手 13 が勝利します。

### 入力例 3

4
6 13 12 5 3 7 10 11 16 9 8 15 2 1 14 4


### 出力例 3

2


Score : 300 points

### Problem Statement

2^N players, labeled 1 through 2^N, will compete against each other in a single-elimination programming tournament.
The rating of Player i is A_i. Any two players have different ratings, and a match between two players always results in the victory of the player with the higher rating.

The tournament looks like a perfect binary tree.
Formally, the tournament will proceed as follows:

• For each integer i = 1, 2, 3, \dots, N in this order, the following happens.
• For each integer j (1 \le j \le 2^{N - i}), among the players who have never lost, the player with the (2j - 1)-th smallest label and the player with the 2j-th smallest label play a match against each other.

Find the label of the player who will take second place, that is, lose in the final match.

### Constraints

• 1 \le N \le 16
• 1 \le A_i \le 10^9
• A_i are pairwise different.
• All values in input are integers.

### Input

Input is given from Standard Input in the following format:

N
A_1 A_2 A_3 \dots A_{2^N}


### Output

Print the label of the player who will take second place.

### Sample Input 1

2
1 4 2 5


### Sample Output 1

2


First, there will be two matches between Players 1 and 2 and between Players 3 and 4. According to the ratings, Players 2 and 4 will win.
Then, there will be a match between Players 2 and 4, and the tournament will end with Player 4 becoming champion.
The player who will lose in the final match is Player 2, so we should print 2.

### Sample Input 2

2
3 1 5 4


### Sample Output 2

1


First, there will be two matches between Players 1 and 2 and between Players 3 and 4. According to the ratings, Players 1 and 3 will win.
Then, there will be a match between Players 1 and 3, and the tournament will end with Player 3 becoming champion.
The player who will lose in the final match is Player 1, so we should print 1.

### Sample Input 3

4
6 13 12 5 3 7 10 11 16 9 8 15 2 1 14 4


### Sample Output 3

2