#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

class union_find {
  public:
    union_find(int n) : data(n, -1) {}
    int unite(int x, int y) {
        x = root(x), y = root(y);
        if(x != y) {
            if(size(x) < size(y)) swap(x, y);
            data[x] += data[y];
            return data[y] = x;
        }
        return -1;
    }
    int root(int x) { return data[x] < 0 ? x : data[x] = root(data[x]); }
    int size(int x) { return -data[root(x)]; }
    bool same(int x, int y) { return root(x) == root(y); }

  private:
    vector<int> data;
};

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    
    int N,M; cin >> N >> M;
    union_find uf(N);
    vector<int> deg(N, 0);
    rep(_,M) {
        int u,v; cin >> u >> v;
        uf.unite(u, v);
        deg[u]++, deg[v]++;
    }

    int ok = 1, cnt0 = 0;
    rep(i,N) if(deg[i] == 0) cnt0++;
    rep(i,N) if(deg[i] != 0) ok &= uf.size(i) == N - cnt0;
    
    int cnt1 = 0;
    rep(i,N) if(deg[i] % 2 == 1) cnt1++;
    ok &= (cnt1 == 0 || cnt1 == 2);

    cout << (ok ? "YES" : "NO") << endl;
}