#include<bits/stdc++.h>
#define ll long long
#define fr(i,x,y) for(int i=(x);i<=(y);i++)
#define rf(i,x,y) for(int i=(x);i>=(y);i--)
#define frl(i,x,y) for(int i=(x);i<(y);i++)
using namespace std;
const int N=200002;
int n,Q;
ll m;
struct data{
	int x,y,w;
	bool operator < (const data &q)const{ return w<q.w; }
}a[N];
int f[N];

template<class T> void read(T &x){
	char ch=getchar();x=0;
	for(;ch<'0'||ch>'9';ch=getchar());
	for(;ch>='0'&&ch<='9';ch=getchar()) x=(x<<3)+(x<<1)+ch-'0';
}

int gf(int x){ return f[x]==x?x:f[x]=gf(f[x]); }

int main(){
	read(n);read(m);read(Q);
	fr(i,1,Q) read(a[i].x),read(a[i].y),read(a[i].w);
	fr(i,1,Q) a[i].x++,a[i].y++;
	sort(a+1,a+1+Q);
	fr(i,1,n) f[i]=i;
	int flag=0;
	fr(i,1,Q){
		if (a[i].w){
			flag=i;
			break;
		}
		int x=a[i].x,y=a[i].y;
		f[gf(x)]=gf(y);
	}
	if (flag) fr(i,flag,Q) if (gf(a[i].x)==gf(a[i].y)) return puts("No"),0;
	int cnt=0;
	fr(i,1,n) if (gf(i)==i) cnt++;
	if (!flag){
		if (m>1LL*cnt*(cnt-1)/2+n-cnt) puts("No");
		 else puts("Yes");
	} else{
		if (cnt<=2||m<n) puts("No");
		 else if (m>1LL*cnt*(cnt-1)/2+n-cnt) puts("No");
		  else puts("Yes");
	}
	return 0;
}