Description

Input

The first line of the input contains two integers $n$ and $m$ ($2 \le n \le 300\,000$, $1 \le m \le 300\,000$) — the number of cities and the number of one-way roads.

Next $m$ lines describe the road system of the kingdom. Each of them contains two integers $u_i$ and $v_i$ ($1 \le u_i, v_i \le n$, $u_i \neq v_i$), denoting one-way road from $u_i$ to $v_i$.

It is guaranteed, that the kingdoms' roads make an acyclic graph, which doesn't contain multiple edges and self-loops.

Output

Print a single integer — the number of cities that the king has to upgrade.

Samples

7 7
1 2
2 3
3 4
4 7
2 5
5 4
6 4

4

6 7
1 2
2 3
3 4
1 5
5 3
2 6
6 4

4

Note

In the first example:

• Starting at the city $1$ we can reach all the other cities, except for the city $6$. Also, from the city $6$ we cannot reach the city $1$. Therefore, if we destroy the city $6$ then the city $1$ will become important. So $1$ is a semi-important city.
• For city $2$, the set of cities that cannot reach $2$ and cannot be reached by $2$ is $\{6\}$. Therefore, destroying city $6$ will make the city $2$ important. So city $2$ is also semi-important.
• For city $3$, the set is $\{5, 6\}$. As you can see, destroying either city $5$ or $6$ will not make the city $3$ important. Therefore, it is neither important nor semi-important.
• For city $4$, the set is empty. So $4$ is an important city.
• The set for city $5$ is $\{3, 6\}$ and the set for city $6$ is $\{3, 5\}$. Similarly to city $3$, both of them are not important nor semi-important.
• The city $7$ is important since we can reach it from all other cities.

So we have two important cities ($4$ and $7$) and two semi-important cities ($1$ and $2$).

In the second example, the important cities are $1$ and $4$. The semi-important cities are $2$ and $3$.