A: Test
Problem
  In a classroom with $N$ seats in a straight line, $M$ students are going to take a test.
  Each seat is numbered from $1 \dots N$, and one student can sit in one seat.
  At this moment, each student sits in seat $A_1, \dots, A_M$.
  To start the test, the following condition must be satisfied.
  
There must be at least one student in every seat from $1 \dots M$.
  Therefore, we decided to repeat the following operation until the condition is satisfied.
  
Move the student who is sitting at the rearmost position to the frontmost available seat.
  Find the number of operations required to satisfy the condition.
Constraints
All input values are integers.
$1 \leq N \leq 1000$
$1 \leq M \leq N$
$1 \leq A_i \leq N$
If $1 \leq i < j \leq M$, then $A_i < A_j$
Input Format
 The input is given in the following format. 
  $N\ M$
  $A_1 \dots A_M$
Output
Output the number of operations required to satisfy the condition, followed by a newline character. 
Sample
Sample Input 1
6 4
1 4 5 6
Sample Output 1
2
Sample Input 2
10 3
1 2 3
Sample Output 2
0
