CF505D Mr. Kitayuta's Technology

Shuseki Kingdom is the world's leading nation for innovation and technology. There are $ n $ cities in the kingdom, numbered from $ 1 $ to $ n $ . Thanks to Mr. Kitayuta's research, it has finally become possible to construct teleportation pipes between two cities. A teleportation pipe will connect two cities unidirectionally, that is, a teleportation pipe from city $ x $ to city $ y $ cannot be used to travel from city $ y $ to city $ x $ . The transportation within each city is extremely developed, therefore if a pipe from city $ x $ to city $ y $ and a pipe from city $ y $ to city $ z $ are both constructed, people will be able to travel from city $ x $ to city $ z $ instantly. Mr. Kitayuta is also involved in national politics. He considers that the transportation between the $ m $ pairs of city $ (a_{i},b_{i}) $ ( $ 1

The first line contains two space-separated integers $ n $ and $ m $ ( $ 2

Print the minimum required number of teleportation pipes to fulfill Mr. Kitayuta's purpose.

For the first sample, one of the optimal ways to construct pipes is shown in the image below: For the second sample, one of the optimal ways is shown below: