// Problem: G - The Only Way to the Destination
// Contest: Virtual Judge - 第九届中国大学生程序设计竞赛 哈尔滨站（CCPC 2023 Harbin Site）
// URL: https://vjudge.net/contest/658339#problem/G
// Memory Limit: 507 MB
// Time Limit: 1000 ms
// 
// Powered by CP Editor (https://cpeditor.org)

#include <bits/stdc++.h>
using namespace std;
#define LL long long
#define pb push_back
#define x first
#define y second 
#define endl '\n'
const LL maxn = 4e05+7;
const LL N = 5e05+10;
const LL mod = 1e09+7;
const int inf = 0x3f3f3f3f;
const LL llinf = 5e18;
typedef pair<int,int>pl;
priority_queue<LL , vector<LL>, greater<LL> >mi;//小根堆
priority_queue<LL> ma;//大根堆
struct Point{
	int x1 , x2 , y , id;
};
void solve() 
{
	int n , m , k;
	cin >> n >> m >> k;	
	int idx = 0;
	if(k * 3 < m){
		cout << "NO\n";
	}
	else{
		//判环
		vector<Point>p;
		vector<int> edge[m + k * 3 + 5];	
		array<int,3> wall[k];
		for(int i = 0 ; i < k ; i ++){
			cin >> wall[i][1] >> wall[i][2] >> wall[i][0];
		}
		sort(wall , wall + k);
		int top = 0;
		int l = 1;
		int ll = 0;
		p.pb({0 , 0 , 0 , 0});
		for(int i = 1 ; i <= m ; i ++){
			int top = 0;
			while(ll < k && wall[ll][0] <= i){
				if(wall[ll][1] == 1){
					top = wall[ll][2];
					ll++;
					break;
				}
				p.pb({top + 1 , wall[ll][1] - 1 , i , ++idx});
				int f = 0;
				while(l < idx && p[idx].y - p[l].y > 1){
					l++;
				}
				while(l < idx && p[idx].y - p[l].y == 1){
					if(p[l].x2 < p[idx].x1){
						l++;
						continue;
					}
					int mi = max(p[l].x1 , p[idx].x1);
					int mx = min(p[l].x2 , p[idx].x2);
					if(mx > mi && p[l].x2 - p[l].x1 > 1 && p[idx].x2 - p[idx].x1 > 1){
						cout << "NO\n";
						return;
					}
					edge[l].pb(idx);
					edge[idx].pb(l);
			//		cout << l << " " << idx << endl;
					l++;
					f = 1;
				}
				if(f){
					l--;
				}
				top = wall[ll][2];
				ll++;
			}
			if(top != n){
				p.pb({top + 1 , n , i , ++idx});
				int f = 0;
				while(l < idx && p[idx].y - p[l].y > 1){
					l++;
				}
				while(l < idx && p[idx].y - p[l].y == 1){
					if(p[l].x2 < p[idx].x1){
						l++;
						continue;
					}
					int mi = max(p[l].x1 , p[idx].x1);
					int mx = min(p[l].x2 , p[idx].x2);
					if(mx > mi && p[l].x2 - p[l].x1 > 1 && p[idx].x2 - p[idx].x1 > 1){
						cout << "NO\n";
						return;
					}
					edge[l].pb(idx);
					edge[idx].pb(l);
					l++;
					f = 1;
				}
				if(f){
					l--;
				}
			}
		}
/*		for(int i = 1 ; i <= idx; i ++){
			for(auto it : edge[i]){
				cout << i << " " << it << endl;
			}
		}*/
		vector<int>adj(idx + 5 , 0);
		for(int i = 1 ; i <= idx ; i ++){
			for(auto it : edge[i]){
				adj[it]++;
			//	cout << i << " " << it << endl;
			}
		}
		queue<int>q;
		for(int i = 1 ; i <= idx ; i ++){
			if(adj[i] == 1){
				q.push(i);
			}
		}		
		while(!q.empty()){
			int x = q.front();
			q.pop();
			for(auto it : edge[x]){
				adj[it]--;
				if(adj[it] == 1){
					q.push(it);
				}
			}
		}
		for(int i = 1 ; i <= idx ; i ++){
			if(adj[i] > 0){
				cout << "NO\n";
				return;
			}
		}
		cout <<"YES\n";
	}
}            
int main() 
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cout.precision(10);
    int t=1;
	//cin>>t;
    while(t--)
    {
    	solve();
    }
    return 0;
}