#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define rng(i,c,n) for(int i=c;i<n;i++)
#define fi first
#define se second
#define pb push_back
#define sz(a) ((int) a.size())
#define all(a) a.begin(), a.end()
#define vec(...) vector<__VA_ARGS__>
typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pii;
void print(){cout<<'\n';}
template<class h,class...t>
void print(const h&v,const t&...u){cout<<v<<' ',print(u...);}

#define unique(a) sort(all(a)); a.erase(unique(all(a)),a.end());

#define yare cout<<"YES\n"; exit(0);

#define nare cout<<"NO\n"; exit(0);

void slv(){
	int n,m,k;
	cin>>n>>m>>k;

	vec(array<int,3>) a;
	rep(i,k){
		int l,r,y;
		cin>>l>>r>>y;
		l-=1,r-=1,y-=1;
		a.pb({y,l,r});
	}

	if(m>2*k+1){
		nare;
	}

	if(n==1){
		yare;
	}

	vec(vec(pii)) ranges(m);
	rep(i,k){
		auto [y,l,r]=a[i];
		ranges[y].pb({l,r});
	}

	rep(i,m){
		vec(pii) tmp;
		sort(all(ranges[i]));
		// for(auto p:ranges[i]){
		// 	print(p.fi,p.se);
		// }
		if(!sz(ranges[i])){
			tmp.pb({0,n-1});
		}else{
			if(ranges[i][0].fi>0){
				tmp.pb({0,ranges[i][0].fi-1});
			}
			if(ranges[i].back().se<n-1){
				tmp.pb({ranges[i].back().se+1,n-1});
			}
			rng(j,1,sz(ranges[i])){
				if(ranges[i][j-1].se+1<=ranges[i][j].fi-1){
					tmp.pb({ranges[i][j-1].se+1,ranges[i][j].fi-1});
				}
			}
		}
		ranges[i]=tmp;
	}

	int si=0;
	rep(i,m){
		si+=sz(ranges[i]);
	}

	vec(vi) adj(si);
	auto add_edge=[&](int u,int v){
		adj[u].pb(v);
		adj[v].pb(u);
	};

	int ptr=0;
	map<pii,int> mp;
	auto id=[&](int i,int j){
		if(mp.find({i,j})==mp.end()){
			return mp[{i,j}]=ptr++;
		}
		return mp[{i,j}];
	};

	auto intersection=[&](pii p,pii q)->pii{
		p.fi=max(p.fi,q.fi);
		p.se=min(p.se,q.se);
		if(p.fi>p.se) return {-1,-1};
		return p;
	};

	// rep(i,m){
	// 	print(" colc ",i);
	// 	for(auto [l,r]:ranges[i]){
	// 		print(l,r);
	// 	}
	// 	print(" ~ ~");
	// }

	rng(i,1,m){
		int j=0;
		rep(j1,sz(ranges[i])){
			pii p=ranges[i][j1];
			while(j<sz(ranges[i-1]) and ranges[i-1][j].se<p.fi){
				j+=1;
			}
			while(j<sz(ranges[i-1])){
				pii cur=intersection(ranges[i-1][j],p);
				if(cur.fi==-1) break;
				if(cur.se-cur.fi+1>1){
					nare;
				}
				// add_edge
				add_edge(id(i,j1),id(i-1,j));
				j+=1;
			}
			if(j) j-=1;
			if(j) j-=1;
		}
	}

	if(si){
		vi usd(si);
		auto dfs=[&](auto self,int v,int par)->void{
			usd[v]=1;
			for(auto u:adj[v]){
				if(u==par) continue;
				if(usd[u]){
					nare;
				}
				self(self,u,v);
			}
		};
		dfs(dfs,0,-1);
	}
	yare;
}

signed main(){
	ios::sync_with_stdio(0),cin.tie(0);
	slv();
}