#pragma GCC target("avx2")
#pragma GCC optimize("03")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std; typedef long double ld; typedef long long ll;
typedef unsigned long long ull;
#define endl "\n"
#define FOR(i,a,b) for(int i=(a);i<=(b);i++)
#define rep(i,n) for(int i=0;i<(n);i++)
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define ALL(x) (x).begin(), (x).end()
constexpr int INF=1<<30; constexpr ll LINF=1LL<<60; constexpr ll mod=1e9+7; constexpr int NIL = -1;
template<class T>inline bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>inline bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
template<class T>inline int popcount(T a) {return __builtin_popcount(a);}
template<class T>inline T emod(T a, T p) { return (a%p + p) % p;}
//-------------------
constexpr int MX = 502;
int G[MX][MX];
int n,m;

class UnionFind {
private:
	unsigned size_; std::vector<int> par, rank; //par = root? -size: par 
public:
	UnionFind() : size_(0), par(std::vector<int>()), rank(std::vector<int>()) {};
	UnionFind(unsigned size__) : size_(size__) {
		par.resize(size_+1); rank.resize(size_+1);
		for (unsigned i = 0; i <= size_; i++) par[i] = -1, rank[i] = 0;
	}
	//unsigned size() { return size_; }
	unsigned root(unsigned x) {return par[x] < 0 ? x : par[x] = root(par[x]); }
	bool same(unsigned x, unsigned y) { return root(x) == root(y); }
	void unite(unsigned x, unsigned y) {
		x = root(x), y = root(y);
		if (x == y) return;
		if (rank[x] < rank[y])par[y] += par[x], par[x] = y;
		else if (rank[x] == rank[y])par[x] += par[y], par[y] = x, rank[x]++;
		else par[x] += par[y], par[y] = x;
	}
	int size(int x){ return -par[root(x)];} 
	bool operator==(const UnionFind &u) { return par == u.par; }
	bool operator!=(const UnionFind &u) { return par != u.par; }
};
int main() {
    cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(15);
    cin >> n >> m;

    UnionFind uf(n);
    unordered_map<int, int> mp;
    rep(i,m) {
        int a,b; cin >> a >> b;
        G[a][b] = 1;
        G[b][a] = 1;
        uf.unite(a,b);
        mp[a]++;
        mp[b]++;
    }
    int all = 0;
    for(auto &[k,v]: mp) {
        if(v>0) all++;
    }
    rep(i, n) {
        if(uf.size(i) == 1 or uf.size(i) == all) continue;
        cout << "NO" << endl;
        return 0;
    }
    int cnt = 0;
    rep(i, n) {
        int cur = 0;
        rep(j, n) {
            cur += G[i][j]==1? 1:0;
        }
        cnt += cur&1? 1: 0;
    }
    if(cnt==0 || cnt ==2) cout << "YES" << endl;
    else cout << "NO" << endl;
    return 0;
}