#include //#include //#include //#include #define rep(i, a) for (int i = (int)0; i < (int)a; ++i) #define rrep(i, a) for (int i = (int)a - 1; i >= 0; --i) #define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i) #define RREP(i, a, b) for (int i = (int)a - 1; i >= b; --i) #define repl(i, a) for (ll i = (ll)0; i < (ll)a; ++i) #define pb push_back #define eb emplace_back #define all(x) x.begin(), x.end() #define rall(x) x.rbegin(), x.rend() #define popcount __builtin_popcount #define fi first #define se second using ll = long long; constexpr ll mod = 1e9 + 7; constexpr ll mod_998244353 = 998244353; constexpr ll INF = 1LL << 60; // #pragma GCC target("avx2") // #pragma GCC optimize("O3") // #pragma GCC optimize("unroll-loops") //using lll=boost::multiprecision::cpp_int; //using Double=boost::multiprecision::number>;//仮数部が1024桁 template inline bool chmin(T &a, T b) { if (a > b) { a = b; return true; } return false; } template inline bool chmax(T &a, T b) { if (a < b) { a = b; return true; } return false; } template T mypow(T x, T n, const T &p = -1) { //x^nをmodで割った余り if (p != -1) { x %= p; } T ret = 1; while (n > 0) { if (n & 1) { if (p != -1) ret = (ret * x) % p; else ret *= x; } if (p != -1) x = (x * x) % p; else x *= x; n >>= 1; } return ret; } using namespace std; //using namespace atcoder; struct UF{ vectorpar,sz; UF(int n){ par.resize(n); sz.resize(n,1); rep(i,n)par[i]=i; } int find(int x){ if(par[x]==x)return x; else return par[x]=find(par[x]); } void unite(int x,int y){ x=find(x),y=find(y); if(x==y)return; if(sz[x]>sz[y]){ sz[x]+=sz[y]; par[y]=par[x]; }else{ sz[y]+=sz[x]; par[x]=par[y]; } } bool same(int x,int y){ return find(x)==find(y); } }; void solve() { int n,m; cin>>n>>m; vector>g(n); vectorconnected(n); UF tree(n); int p; rep(i,m){ int a,b; cin>>a>>b; connected[a]=1; connected[b]=1; tree.unite(a,b); g[a].eb(b); g[b].eb(a); p=a; } int sum=accumulate(all(connected),0); if(sum!=tree.sz[tree.find(p)]){ cout<<"NO\n"; return; } int cnt=0; rep(i,n)if(g[i].size()%2)++cnt; if(cnt==2||cnt==0){ cout<<"YES\n"; }else{ cout<<"NO\n"; } } int main() { ios::sync_with_stdio(false); cin.tie(nullptr); cout << fixed << setprecision(15); solve(); return 0; }