forestsize

Problem Statement

You a given a undirected forest graph (see definition below) with $n$ nodes and $m$ edges. Determine the number of trees in the forest graph.

NOTE: A forest graph is a graph containing multiple disconnected trees. Also think twice before starting to code.

Input Format

Your first line will contain two integers $n$ and $m$. Your next $m$ lines will contain two integers each, $u$ and $v$ denoting that $u$ has an undirected edge to $v$. You are guaranteed these edges will form a forest graph.

Output Format

Output a single integer, the number of trees of disconnected trees in the forest graph.

Constraints

• $1 \leq n \leq 10^5$
• $0 \leq m \lt n - 1$
• $0 \leq u, v \lt n$
• You are guaranteed there are no repeated edges.
• You are guaranteed the edges will form a forest graph.

Sample Cases

5 3
0 1
1 2
3 4

2

Notice there are two trees in this forest, one is formed by the nodes $\{0, 1, 2\}$ and the other by the nodes $\{3, 4\}$.

10 6
7 0
1 4
0 1
1 2
1 3
7 8

4

Here we can notice that a lot of the trees are single nodes, in particular nodes $5$, $6$ and $9$ have no edges and are their own trees, all other nodes form a single tree.