#include<bits/stdc++.h>
#define L first
#define R second
#define pii pair<int,int>
using namespace std;
const int N=1e6+5;
int n,m,k;
int p[N];
int fl[N];
int x1[N],x2[N],y[N];
int fa[N];
vector<pii>s1[N],s2[N],s[N];
int find(int x){return fa[x]==x?x:fa[x]=find(fa[x]);}
bool merge(int x,int y){
	x=find(x),y=find(y);
	if(x==y)return 0;
	else {fa[x]=y;return 1;}
}
void work(int id){
	sort(s1[id].begin(),s1[id].end());
	s2[id].push_back(s1[id][0]);
	int now=0;
	for(int i=1;i<(int)s1[id].size();i++){
		if(s1[id][i].L>s2[id][now].R+1)
			now++,s2[id].push_back(s1[id][i]);
		else s2[id][now].R=s1[id][i].R;
	}
	if(s2[id][0].L!=1)s[id].push_back(pii(1,s2[id][0].L-1));
	if(s2[id][now].R!=n)s[id].push_back(pii(s2[id][now].R+1,n));
	for(int i=0;i<=now-1;i++){
		int l=s2[id][i].R+1;
		int r=s2[id][i+1].L-1;
		if(l<=r)s[id].push_back(pii(l,r));
	}
	sort(s[id].begin(),s[id].end());
}
int ck(int l1,int r1,int l2,int r2){
	int L=max(l1,l2);
	int R=min(r1,r2);
	return max(R-L+1,0);
}
int main(){
	scanf("%d%d%d",&n,&m,&k);
	for(int i=1;i<=k;i++){
		scanf("%d%d%d",&x1[i],&x2[i],&y[i]);
		p[i]=y[i];
	}
	if(m>=3e5+1||){puts("NO");return 0;}
	sort(p+1,p+k+1);
	int kk=unique(p+1,p+k+1)-p-1;
	for(int i=1;i<=kk;i++)fl[p[i]]=i;
	for(int i=1;i<=kk;i++)
		if(p[i]-p[i-1]>=3){puts("NO");return 0;}
	if((m+1)-p[kk]>=3){puts("NO");return 0;}
	for(int i=1;i<=k;i++){
		int id=fl[y[i]];
		s1[id].push_back(pii(x1[i],x2[i]));
	}
	for(int i=1;i<=kk;i++)work(i);
	for(int i=1;i<N;i++)fa[i]=i;
	int sm=0;
	s[0].push_back(pii(1,n));
	for(int i=2;i<=m;i++){
		int id1=fl[i-1],id2=fl[i];
		int sz1=s[id1].size(),sz2=s[id2].size();
		for(int t1=0;t1<sz1;t1++)
			for(int t2=0;t2<sz2;t2++){
				int l1=s[id1][t1].L,r1=s[id1][t1].R;
				int l2=s[id2][t2].L,r2=s[id2][t2].R;
				int num=ck(l1,r1,l2,r2);
				if(num>=2){puts("NO");return 0;}
				if(num==1){
					int X=sm+t1+1,Y=sm+sz1+1+t2;
					bool fl=merge(X,Y);
					if(!fl){puts("NO");return 0;}
				}
			}
		sm+=s[fl[i-1]].size();
	}
	puts("YES");
	return 0;
}
/*
5 3 1
2 4 2
*/

answer.code: In function ‘int main()’:
answer.code:48:22: error: expected primary-expression before ‘)’ token
   48 |         if(m>=3e5+1||){puts("NO");return 0;}
      |                      ^
answer.code:43:14: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   43 |         scanf("%d%d%d",&n,&m,&k);
      |         ~~~~~^~~~~~~~~~~~~~~~~~~
answer.code:45:22: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   45 |                 scanf("%d%d%d",&x1[i],&x2[i],&y[i]);
      |                 ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~