#include <bits/stdc++.h>
using namespace std;
#define x first
#define y second
#define endl '\n'
#define int long long
typedef long double f128;
typedef long long i64;
typedef unsigned long long u64;
typedef pair<int, int> pii;
const int INF = 0x3f3f3f3f, mod = 1e9 + 7;
const i64 inf = 2e18;
//-------------------------------------------
struct node
{
    int l, r, y;
};

void solve()
{
    int n, m, k;
    cin >> n >> m >> k;
    vector<node> g;
    vector<int> a;
    for (int i = 1; i <= k; i++)
    {
        int l, r, y;
        cin >> l >> r >> y;
        a.push_back(y);
        g.push_back({l, r, y});
    }

    g.push_back({1, n, 0});
    g.push_back({1, n, m + 1});
    a.push_back(m + 1);
    sort(g.begin(), g.end(), [&](node a, node b)
         {
        if (a.y != b.y)
          return a.y < b.y;
        return a.l < b.l; });

    sort(a.begin(), a.end());
    a.erase(unique(a.begin(), a.end()), a.end());
    int l = 1;
    for (auto t : a)
    {
        if (t - l - 1 >= 2)
        {
            cout << "NO" << endl;
            return;
        }
        l = t;
    }

    vector<pii> v[2];
    vector<int> col[2];
    int p = 0;

    for (int i = 1; i <= m; i++)
    {
        int id = i % 2;
        int l = 1;
        v[id].clear();
        for (; p < g.size(); p++)
        {
            if (g[p].y == i)
            {
                if (l < g[p].l)
                    v[id].push_back({l, g[p].l - 1});
                l = g[p].r + 1;
            }
            else if (g[p + 1].y > i)
                break;
        }
        if (l <= n)
            v[id].push_back({l, n});
        col[id].resize(v[id].size(), -1);
        int id1 = 0;
        for (int j = 0; j < v[id].size(); j++)
        {
            auto t = v[id][j];
            while (id1 + 1 < v[id ^ 1].size() && v[id ^ 1][id1].y < t.x)
                id1++;
            while (id1 < v[id ^ 1].size())
            {
                //cerr << v[id ^ 1][id1].x << " " << v[id ^ 1][id1].y << " " << col[id][j] << endl;
                if (col[id][j] == col[id ^ 1][id1])
                {
                    cout << "NO" << endl;
                    return;
                }
                else
                {
                    col[id][j] = col[id ^ 1][id1];
                }

                //if (id1 + 1 < v[id ^ 1].size() && v[id ^ 1][id1].y <= t.y)
                    id1++;
            }
            int mex = 0;
            for (int j = 0; j < v[id].size(); j++)
            {
                while (mex == col[id][j])
                    mex++;
                col[id][j] = mex;
            }
        }
    }

    cout << "YES" << endl;
}
signed main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int T = 1;
    // cin >> T;
    for (int i = 1; i <= T; i++)
        solve();
    return 0;
}