Problem:
Score : 400 points

Problem Statement

There are N persons called Person 1 through Person N.

You are given M facts that "Person A_i and Person B_i are friends." The same fact may be given multiple times.

If X and Y are friends, and Y and Z are friends, then X and Z are also friends. There is no friendship that cannot be derived from the M given facts.

Takahashi the evil wants to divide the N persons into some number of groups so that every person has no friend in his/her group.

At least how many groups does he need to make?

Constraints

2 \leq N \leq 2\times 10^5

0 \leq M \leq 2\times 10^5

1\leq A_i,B_i\leq N

A_i \neq B_i

Input

Input is given from Standard Input in the following format:

N M
A_1 B_1
\vdots
A_M B_M

Output

Print the answer.

Sample Input 1

5 3
1 2
3 4
5 1

Sample Output 1

3

Dividing them into three groups such as \{1,3\}, \{2,4\}, and \{5\} achieves the goal.

Sample Input 2

4 10
1 2
2 1
1 2
2 1
1 2
1 3
1 4
2 3
2 4
3 4

Sample Output 2

4

Sample Input 3

10 4
3 1
4 1
5 9
2 6

Sample Output 3

3

Solution in Rust (1.42.0) (judge verdict: Accepted)

pub struct ProconReader<R: std::io::Read> {
    reader: R,
}

impl<R: std::io::Read> ProconReader<R> {
    pub fn new(reader: R) -> Self {
        Self { reader }
    }
    pub fn get<T: std::str::FromStr>(&mut self) -> T {
        use std::io::Read;
        let buf = self
            .reader
            .by_ref()
            .bytes()
            .map(|b| b.unwrap())
            .skip_while(|&byte| byte == b' ' || byte == b'\n' || byte == b'\r')
            .take_while(|&byte| byte != b' ' && byte != b'\n' && byte != b'\r')
            .collect::<Vec<_>>();
        std::str::from_utf8(&buf)
            .unwrap()
            .parse()
            .ok()
            .expect("Parse Error.")
    }
}

pub struct UnionFind {
    par: Vec<usize>,
    size: Vec<usize>,
}

impl UnionFind {
    pub fn new(n: usize) -> UnionFind {
        UnionFind {
            par: (0..n).map(|i| i).collect::<Vec<_>>(),
            size: vec![1; n],
        }
    }
    pub fn find(&mut self, i: usize) -> usize {
        if self.par[i] == i {
            self.par[i]
        } else {
            self.par[i] = self.find(self.par[i]);
            self.par[i]
        }
    }
    pub fn unite(&mut self, i: usize, j: usize) {
        let i = self.find(i);
        let j = self.find(j);
        if i == j {
            return;
        }
        let (i, j) = if self.size[i] >= self.size[j] {
            (i, j)
        } else {
            (j, i)
        };
        self.par[j] = i;
        self.size[i] += self.size[j];
    }
    pub fn get_size(&mut self, i: usize) -> usize {
        let p = self.find(i);
        self.size[p]
    }
}

fn main() {
    let stdin = std::io::stdin();
    let mut rd = ProconReader::new(stdin.lock());

    let n: usize = rd.get();
    let m: usize = rd.get();
    let ab: Vec<(usize, usize)> = (0..m)
        .map(|_| {
            let a: usize = rd.get();
            let b: usize = rd.get();
            (a - 1, b - 1)
        })
        .collect();

    let mut uf = UnionFind::new(n);
    for (a, b) in ab {
        uf.unite(a, b);
    }
    let size = (0..n).map(|i| uf.get_size(i)).max().unwrap();
    println!("{}", size);
}