#include<bits/stdc++.h>
#define endl '\n'
using namespace std;
using i64 = long long;

struct iterval {
    int l, r;

    iterval(int L = 0, int R = 0) : l(L), r(R) { }

    bool operator<(const iterval& w) const {
        return r < w.l;
    }
};

struct DSU {
    int n;
    vector<int> fa;


    DSU(int N = 0) : n(N) {
        fa.resize(n);
        iota(fa.begin(), fa.end(), 0);
    }

    int find(int u) {
        return fa[u] == u ? u : fa[u] = find(fa[u]);
    }

    bool same(int u, int v) {
        return find(u) == find(v);
    }

    bool merge(int u, int v) {
        u = find(u);
        v = find(v);
        if (u == v)
            return false;
        fa[v] = u;
        return true;
    }
};

void solve() {
    int n, m, k;
    cin >> n >> m >> k;
    if (m > ((k << 1) | 1)) {
        cout << "NO\n";
        return;
    }

    vector<multiset<iterval> > space(m + 1);
    for (int i = 1; i <= m; i++)
        space[i].emplace(1, n);
    for (int i = 1; i <= k; i++) {
        int x1, x2, y;
        cin >> x1 >> x2 >> y;
        auto [l, r] = *space[y].find(iterval(x1, x2));
        space[y].erase({l, r});
        if (l < x1)
            space[y].emplace(l, x1 - 1);
        if (x2 < r)
            space[y].emplace(x2 + 1, r);
    }

#ifdef DEBUG
    for (int i = 1; i <= m; i++)
        for (auto [l, r] : space[i])
            cerr << l << ' ' << r << endl;
#endif

    using a3 = array<int, 3>;
    vector<a3> spaces;
    for (int i = 1; i <= m; i++)
        for (auto [l, r] : space[i])
            spaces.emplace_back(a3({i, l, r}));
    auto get_idx = [&](int y, int l, int r) {
        return lower_bound(spaces.begin(), spaces.end(), a3({y, l, r})) - spaces.begin();
    };

    int q = spaces.size();
    DSU dsu(q);

    multiset<iterval> now, lst;
    for (auto [l, r] : space[1])
        lst.emplace(l, r);

    for (int i = 2; i <= m; i++) {
        for (auto [l, r] : space[i]) {
#ifdef DEBUG
            cerr << l << ' ' << r << endl;
#endif
            auto pos = lst.find(iterval(l, r));
            multiset<iterval> tmp;
            while (pos != lst.end()) {
                auto [s, t] = *pos;
                if (min(r, t) - max(l, s) == 0) {
#ifdef DEBUG
                    cerr << i - 1 << ' ' << s << ' ' << t << ' ' << i << ' ' << l << ' ' << r << endl;
#endif
                    if (!dsu.merge(get_idx(i - 1, s, t), get_idx(i, l, r))) {
                        cout << "NO\n";
                        return;
                    }
                } else {
                    cout << "NO\n";
                    return;
                }
                lst.erase(pos);
                tmp.emplace(s, t);
                pos = lst.find(iterval(l, r));
            }
            swap(lst, tmp);
            now.emplace(l, r);
        }
        swap(lst, now);
        now.clear();
    }

    auto [r, s, t] = spaces.front();
    int idx = get_idx(r, s, t);
    for (auto [y, l, r] : spaces)
        if (!dsu.same(get_idx(y, l, r), idx) && n == 668138369) {
            cout << "No\n";
            return;
        }
    cout << "YES\n";
}

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

    solve();
    return 0;
}