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B - Trick Taking

Score : $200$ points

Problem Statement

$N$ players with ID numbers $1, 2, \ldots, N$ are playing a card game.
Each player plays one card.

Each card has two parameters: color and rank, both of which are represented by positive integers.
For $i = 1, 2, \ldots, N$, the card played by player $i$ has a color $C_i$ and a rank $R_i$. All of $R_1, R_2, \ldots, R_N$ are different.

Among the $N$ players, one winner is decided as follows.

• If one or more cards with the color $T$ are played, the player who has played the card with the greatest rank among those cards is the winner.
• If no card with the color $T$ is played, the player who has played the card with the greatest rank among the cards with the color of the card played by player $1$ is the winner. (Note that player $1$ may win.)

Print the ID number of the winner.

Constraints

• $2 \leq N \leq 2 \times 10^5$
• $1 \leq T \leq 10^9$
• $1 \leq C_i \leq 10^9$
• $1 \leq R_i \leq 10^9$
• $i \neq j \implies R_i \neq R_j$
• All values in the input are integers.

Input

The input is given from Standard Input in the following format:

$N$ $T$

$C_1$ $C_2$ $\ldots$ $C_N$

$R_1$ $R_2$ $\ldots$ $R_N$

Output

Print the answer.

4 2
1 2 1 2
6 3 4 5

4

Cards with the color $2$ are played. Thus, the winner is player $4$, who has played the card with the greatest rank, $5$, among those cards.

4 2
1 3 1 4
6 3 4 5

1

No card with the color $2$ is played. Thus, the winner is player $1$, who has played the card with the greatest rank, $6$, among the cards with the color of the card played by player $1$ (color $1$).

2 1000000000
1000000000 1
1 1000000000

1