Contest: Task: Related: TaskA TaskC

Score : $200$ points

There are $N + 1$ squares arranged in a row, numbered $0, 1, ..., N$ from left to right.

Initially, you are in Square $X$. You can freely travel between adjacent squares. Your goal is to reach Square $0$ or Square $N$. However, for each $i = 1, 2, ..., M$, there is a toll gate in Square $A_i$, and traveling to Square $A_i$ incurs a cost of $1$. It is guaranteed that there is no toll gate in Square $0$, Square $X$ and Square $N$.

Find the minimum cost incurred before reaching the goal.

- $1 \leq N \leq 100$
- $1 \leq M \leq 100$
- $1 \leq X \leq N - 1$
- $1 \leq A_1 < A_2 < ... < A_M \leq N$
- $A_i \neq X$
- All values in input are integers.

Input is given from Standard Input in the following format:

$N$ $M$ $X$ $A_1$ $A_2$ $...$ $A_M$

Print the minimum cost incurred before reaching the goal.

5 3 3 1 2 4

1

The optimal solution is as follows:

- First, travel from Square $3$ to Square $4$. Here, there is a toll gate in Square $4$, so the cost of $1$ is incurred.
- Then, travel from Square $4$ to Square $5$. This time, no cost is incurred.
- Now, we are in Square $5$ and we have reached the goal.

In this case, the total cost incurred is $1$.

7 3 2 4 5 6

0

We may be able to reach the goal at no cost.

10 7 5 1 2 3 4 6 8 9

3