use std::collections::{HashSet, BTreeSet, HashMap};

struct UnionFind {
    n: usize,
    parents: Vec<usize>,
    depths: Vec<usize>,
    chains: Vec<usize>,
}

impl UnionFind {
    fn new(n: usize) -> Self {
        UnionFind {
            n: n,
            parents: (0..n).collect(),
            depths: vec![0; n],
            chains: vec![1; n],
        }
    }

    fn equiv(&mut self, a: usize, b: usize) -> bool {
        self.find(a) == self.find(b)
    }
    
    fn unite(&mut self, a: usize, b: usize) {
        if self.equiv(a, b) { return; }
        let x = self.parents[a];
        let y = self.parents[b];
        if self.depths[x] > self.depths[y] {
            self.parents[x] = self.parents[y];
            self.chains[y] += self.chains[x];
        } else {
            self.parents[y] = self.parents[x];
            self.chains[x] += self.chains[y];
            if self.depths[x] == self.depths[y] {
                self.depths[x] += 1;
            }
        }
    }

    fn find(&mut self, a: usize) -> usize {
        if self.parents[a] == a { return a; }
        let p = self.find(self.parents[a]);
        self.parents[a] = p;
        p
    }

    fn chain_cnt(&mut self, i: usize) -> usize {
        let idx = self.find(i);
        self.chains[idx]
    }
}

fn main() {
    let mut nm = String::new();
    std::io::stdin().read_line(&mut nm).ok();
    let nm: Vec<usize> = nm.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();   
    let n = nm[0];
    let m = nm[1];
    let mut btree = BTreeSet::new();
    let mut lines = Vec::with_capacity(m);
    for _ in 0..m {
        let mut temp = String::new();
        std::io::stdin().read_line(&mut temp).ok();
        let temp: Vec<usize> = temp.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
        let a = temp[0];
        let b = temp[1];
        lines.push((a, b));
        btree.insert(a);
        btree.insert(b);
    }

    let mapping = btree.iter().enumerate().map(|(i, &v)| (v, i)).collect::<HashMap<usize, usize>>();
    let mut uf = UnionFind::new(btree.len());
    let mut paths = vec![vec![]; btree.len()];
    for &(l, r) in lines.iter() {
        let l = *mapping.get(&l).unwrap();
        let r = *mapping.get(&r).unwrap();
        paths[l].push(r);
        paths[r].push(l);
        uf.unite(l, r);
    }
    if (0..btree.len()).map(|i| uf.find(i)).collect::<HashSet<usize>>().len() > 1 {
        println!("NO");
        return;
    }
    let cnt = paths.iter().filter(|&v| v.len() % 2 == 1).count();
    if cnt > 2 {
        println!("NO");
    } else {
        println!("YES");
    }
}