#include<cstdio>
#define no return puts("No")&0;
#define yes return puts("Yes")&0;
using namespace std;
const int maxn=100005;
long long m;
int n,Q,cnt,a[maxn],b[maxn],c[maxn],fa[maxn];
inline char nc(){
	static char buf[100000],*p1=buf,*p2=buf;
	return p1==p2&&(p2=(p1=buf)+fread(buf,1,100000,stdin),p1==p2)?EOF:*p1++;
}
inline long long read(){
	long long ret=0;bool f=0;char ch=nc();
	while(ch>'9'||ch<'0') f^=ch=='-',ch=nc();
	while(ch<='9'&&ch>='0') ret=ret*10+ch-'0',ch=nc();
	return f?-ret:ret;
}
int getfa(int x){return fa[x]==x?x:fa[x]=getfa(fa[x]);}
int main(){
	n=read(),m=read(),Q=read();
	for (int i=1;i<=n;i++) fa[i]=i;
	for (int i=1;i<=Q;i++){
		a[i]=read()+1,b[i]=read()+1,c[i]=read();
		if(m==n-1&&c[i]) no
		if(!c[i]){
			int fx=getfa(a[i]),fy=getfa(b[i]);
			if(fx^fy) fa[fx]=fy;
		}
	}
	if(m==n-1) yes
	for (int i=1;i<=Q;i++)
	if(c[i]&&getfa(a[i])==getfa(b[i])) no
	for (int i=1;i<=n;i++)
	cnt+=getfa(i)==i;
	if(cnt<=2) no
	if(m-n<=1ll*cnt*(cnt-3)>>1) yes
	else no
}