Competitions

# Cover graph vertices with non intersecting paths

# Covering with paths

An oriented acyclic graph is given. Find the minimum number of disjoint paths covering all vertices.

#### Input

First line contains number of vertices **n** and number of edges **m** (**2** ≤ **n** ≤ **1000**, **0** ≤ **m** ≤ `10`

). Each of the next ^{5}**m** lines contains two numbers: the numbers of the vertces **u** and **v** connected with an edge (**u**, **v**).

#### Output

Print the minimum number of paths that can cover all the vertices.

Input example #1

3 3 1 3 3 2 1 2

Output example #1

1