#include <bits/stdc++.h>
using namespace std;

#define int long long
#define pii pair<int, int>
#define fi first
#define se second

int n, m, k;
const int N = 2e5 + 10;
struct emp
{
	int l, r, id;
	inline emp(int L = 0, int R = 0, int ID = 0)
	{
		l = L, r = R, id = ID;
	}
};

int fun(emp a, emp b)
{
	int al = a.l, ar = a.r;
	int bl = b.l, br = b.r;
	int mxl = max(al, bl), mnr = min(ar, br);
	return max((int)0, mnr - mxl + 1);
}

vector<int> fa(N);

int find(int x)
{
	while (fa[x] != x)
	{
		x = fa[x];
	}
	return x;
}

signed main()
{
	cin >> n >> m >> k;
	int M = m + 5;
	vector<pii> w[M];
	vector<emp> e[M];
	vector<pii> g;

	for (int i = 1; i <= k; i++)
	{
		int x1, x2, y;
		cin >> x1 >> x2 >> y;
		w[y].push_back({x1, x2});
	}

	if (n == 1)
	{
		cout << "YES" << endl;
		return 0;
	}

	if (m > 2 * k + 1)
	{
		cout << "NO" << endl;
		return 0;
	}

	int idx = 0;
	for (int y = 1; y <= m; y++)
	{
		int l = 1;
		for (int j = 0; j < w[y].size(); j++)
		{
			if (w[y][j].fi - 1 >= l)
			{
				e[y].push_back(emp(l, w[y][j].fi - 1, ++idx));
				// cout << y << ' ' << l << ' ' << w[y][j].fi - 1 << endl;
			}
			l = w[y][j].se + 1;
		}
		if (l <= n)
		{
			e[y].push_back(emp(l, n, ++idx));
			// cout << y << ' ' << l << ' ' << n << endl;
		}
	}

	for (int y = 1; y < m; y++)	
	{
		for (int p = 0, q = 0; p < e[y].size(); p++)
		{
			if (q > 0)
				--q;
			while (q >= 0 && q < e[y + 1].size() && e[y + 1][q].r < e[y][p].l)
				q++;
			// cout << p << ' ' << q << endl;
			while (q >= 0 && q < e[y + 1].size() && fun(e[y][p], e[y + 1][q]) != 0)
			{
				if (fun(e[y][p], e[y + 1][q]) > 1)
				{
					// cout << y << ' ' << p << ' ' << q << ' ' << fun(e[y][p], e[y + 1][q]) << endl;
					cout << "NO" << endl;
					return 0;
				}
				g.push_back({e[y][p].id, e[y + 1][q].id});
				q ++ ;
			}
		}
	}
	
	for (int i = 1; i <= idx; i++)
	{
		fa[i] = i;
	}

	for (auto [u, v] : g)
	{
		if (find(u) == find(v))
		{
			cout << "NO" << endl;
			return 0;
		}
		fa[find(u)] = find(v);
	}
	cout << "YES" << endl;

	return 0;
}