#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; typedef long long ll; typedef unsigned long long ull; typedef pair P; const double PI = 3.14159265358979323846; const double EPS = 1e-12; const ll INF = 1LL<<29; const ll mod = 1e9+7; #define rep(i,n) for(int (i)=0;(i)<(ll)(n);++(i)) #define repd(i,n,d) for(ll (i)=0;(i)<(ll)(n);(i)+=(d)) #define all(v) (v).begin(), (v).end() #define pb(x) push_back(x) #define mp(x,y) make_pair((x),(y)) #define mset(m,v) memset((m),(v),sizeof(m)) #define chmin(X,Y) ((X)>(Y)?X=(Y),true:false) #define chmax(X,Y) ((X)<(Y)?X=(Y),true:false) #define fst first #define snd second #define UNIQUE(x) (x).erase(unique(all(x)),(x).end()) template ostream &operator<<(ostream &os, const vector &v){int n=v.size();rep(i,n)os<>n>>m; rep(i, m){ int a, b; cin>>a>>b; d[a]++; d[b]++; } int odd = 0; rep(i, n) if(d[i]%2) odd++; if(odd>2) cout<<"NO"<