A8963. Multithreading

The first line of input contains an integer $n$ , the number of threads ( $1<=n<=10^{5}$ ). The next line contains a list of $n$ space-separated integers $a_{1}$ , $a_{2}$ , ..., $a_{n}$ where $a_{i}$ ( $1<=a_{i}<=n$ ) is the old position of the $i$ -th thread in the new list. It is guaranteed that all of the $a_{i}$ are distinct.

Output a single integer — the number of threads that surely contain a new message.

In the first test case, threads 2 and 5 are placed before the thread 1, so these threads must contain new messages. Threads 1, 3 and 4 may contain no new messages, if only threads 2 and 5 have new messages.

In the second test case, there may be no new messages at all, since the thread order hasn't changed.

In the third test case, only thread 1 can contain no new messages.

In the first test case, threads 2 and 5 are placed before the thread 1, so these threads must contain new messages. Threads 1, 3 and 4 may contain no new messages, if only threads 2 and 5 have new messages.

In the second test case, there may be no new messages at all, since the thread order hasn't changed.

In the third test case, only thread 1 can contain no new messages.