#include <bits/stdc++.h>

using namespace std;

using ll = long long;

#define int ll
using pii = pair<int, int>;

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

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

    vector<vector<pii>> p(m);

    for (int i = 0; i < k; i++) {
        int x1, x2, y;
        cin >> x1 >> x2 >> y;
        x1--, x2--, y--;
        p[y].push_back({x1, x2});
    }

    for (int i = 0; i < m; i++) {
        sort(p[i].begin(), p[i].end());
    }

    int cnt = 0;
    vector<vector<pii>> gap(m);
    vector<vector<int>> node(m);

    auto insert = [&](int i, int l, int r) -> void {
        if (l > r)
            return;
        gap[i].push_back({l, r});
        node[i].push_back(cnt);
        cnt++;
    };

    for (int i = 0; i < m; i++) {
        if (!p[i].size()) {
            insert(i, 0, n - 1);
        } else {
            insert(i, 0, p[i][0].first - 1);
            for (int j = 1; j < p[i].size(); j++) {
                insert(i, p[i][j - 1].second + 1, p[i][j].first - 1);
            }
            insert(i, p[i][p[i].size() - 1].second + 1, n - 1);
        }
    }

    vector<vector<int>> adj(cnt + 1);

    for (int i = 1; i < m; i++) {
        for (int x = 0, y = 0; x < gap[i - 1].size() && y < gap[i].size(); x++) {
            while (y < gap[i].size() && gap[i][y].second < gap[i - 1][x].first) y++;
            int tmp = y;
            while (tmp < gap[i].size() && gap[i][tmp].first <= gap[i - 1][x].second) {
                if (min(gap[i][tmp].second, gap[i - 1][x].second) - max(gap[i][tmp].first, gap[i - 1][x].first) + 1 >= 2) {
                    // cout << i << "\n";
                    // cout << gap[i][y].first << " " << gap[i][y].second << "\n";
                    // cout << gap[i - 1][x].first << " " << gap[i - 1][x].second << "\n";
                    cout << "NO\n";
                    return;
                }
                adj[node[i][tmp]].push_back(node[i - 1][x]);
                adj[node[i - 1][x]].push_back(node[i][tmp]);
                tmp++;
            }
        }
    }
    // cerr << cnt;
    vector<int> vis(cnt);
    auto dfs = [&](auto dfs, int u, int fa) -> void {
        // cerr << u;
        vis[u] = 1;
        for (auto v : adj[u]) {
            if (v == fa)
                continue;
            if (vis[v]) {
                cout << "NO\n";
                exit(0);
            }
            dfs(dfs, v, u);
        }
    };

    dfs(dfs, 0, -1);
    for (int i = 0; i < cnt; i++) {
        // cerr << vis[i];
        if (!vis[i]) {
            cout << "NO\n";
            return;
        }
    }

    cout << "YES\n";
    return;
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int t = 1;
    // cin >> t;
    while (t--) {
        solve();
    }
}