1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 using namespace std;
 5 const int maxn=5010;
 6 int n,m;
 7 int cnt,fir[maxn],nxt[maxn*600],to[maxn*600];
 8 void addedge(int a,int b){
 9     nxt[++cnt]=fir[a];
10     fir[a]=cnt;
11     to[cnt]=b;
12 }
13 int scc[maxn],scnt;
14 int ID[maxn],low[maxn],tot;
15 int st[maxn],top;
16 
17 void Tarjan(int x){
18     ID[x]=low[x]=++tot;st[++top]=x;
19     for(int i=fir[x];i;i=nxt[i]){
20         if(ID[to[i]]){
21             if(!scc[to[i]])
22                 low[x]=min(low[x],ID[to[i]]);
23         }
24         else{
25             Tarjan(to[i]);
26             low[x]=min(low[x],low[to[i]]);
27         }
28     }
29     if(low[x]==ID[x]){
30         ++scnt;
31         while(true){
32             int y=st[top--];
33             scc[y]=scnt;
34             if(x==y)break;
35         }
36     }    
37 }
38 bool Solve(){
39     for(int i=0;i<2*n;i++)
40         if(!ID[i])Tarjan(i);
41 
42     for(int i=0;i<n;i++)
43         if(scc[i*2]==scc[i*2+1])
44             return false;
45     return true;        
46 }
47 
48 void Init(){
49     memset(fir,0,sizeof(fir));
50     memset(scc,0,sizeof(scc));
51     memset(ID,0,sizeof(ID));
52     cnt=0;tot=0;scnt=0;
53 }
54 
55 int main(){
56     while(scanf("%d%d",&n,&m)!=EOF){
57         Init();
58         while(m--){
59             int a,b,c,d;
60             scanf("%d%d%d%d",&a,&b,&c,&d);
61             a=a*2+c;b=b*2+d;
62             addedge(a,b^1);addedge(b,a^1);
63         }
64         if(Solve())
65             printf("YES\n");
66         else 
67             printf("NO\n");    
68     }
69     return 0;    
70 }