#include <iostream>
using namespace std;
#include <set>
#include <algorithm>
#include <cmath>
#include <map>
#include <cstdio>
#include <string>
#include <cstring>
#include <string.h>
#include <stdlib.h>
#include <iomanip>
#include <fstream>
#include <stdio.h>
#include <stack>
#include <queue>
#include <ctype.h>
#include <vector>
#include <random>
#define ll long long
#define ull unsigned long long
#define pb push_back
#define rep(i, a, n) for (int i = a; i <= n; i++)
#define per(i, a, n) for (int i = n; i >= a; i--)
#define pii pair<int, int>
#define pli pair<ll, int>
#define pil pair<int, ll>
#define endl '\n'
const double pai = acos(-1);
ll extend_gcd(ll a, ll b, ll &x, ll &y)
{
    if (b == 0)
    {
        x = 1;
        y = 0;
        return a;
    }
    ll d = extend_gcd(b, a % b, y, x);
    y -= a / b * x;
    return d;
}
ll fastpow(ll a, ll n, ll mod)
{
    ll ans = 1;
    a %= mod;
    while (n)
    {
        if (n & 1)
            ans = (ans * a) % mod; //% mod
        a = (a * a) % mod;         //% mod
        n >>= 1;
    }
    return ans;
}
int dir[4][2] =
    {
        {0, 1}, {0, -1}, {1, 0}, {-1, 0}}; // d a w s

const double inf = 1000000000000000000;
const ll mod = 1e9 + 7, P1 = 13331;
const double eps = 1e-7;
const int N = 3e5 + 10, M = 1e6 + 10;

int hang, lie, k;

struct node
{
    int x1, x2;
    node(int a, int b)
    {
        x1 = a;
        x2 = b;
    }
};

bool cmp(node a, node b)
{
    return a.x1 < b.x1;
}

vector<node> v[N], w[N];

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    // freopen("ain.txt", "r", stdin);freopen("aout.txt", "w", stdout);
    cin >> hang >> lie >> k;
    if (hang == 1)
    {
        cout << "YES";
        exit(0);
    }
    if (lie >= 2 * (k + 1))
    {
        cout << "NO";
        exit(0);
    }
    rep(i, 1, k)
    {
        int x1, x2, y;
        cin >> x1 >> x2 >> y;
        v[y].pb(node(x1, x2));
    }
    rep(i, 1, lie)
    {
        sort(v[i].begin(), v[i].end(), cmp);
    }
    int dian = 0, bian = 0;
    rep(i, 1, lie)
    {
        if (v[i].size() == 0)
        {
            w[i].pb(node(1, hang));
            dian++;
        }
        else
        {
            int siz = v[i].size();
            if (v[i][0].x1 != 1)
            {
                w[i].pb(node(1, v[i][0].x1 - 1));
                dian++;
            }
            rep(j, 0, siz - 2)
            {
                int qian = v[i][j].x2 + 1;
                int hou = v[i][j + 1].x1 - 1;
                if (qian <= hou)
                {
                    w[i].pb(node(qian, hou));
                    dian++;
                }
            }
            if (v[i][siz - 1].x2 != hang)
            {
                w[i].pb(node(v[i][siz - 1].x2 + 1, hang));
                dian++;
            }
        }
    }
    rep(i, 1, lie - 1)
    {
        if (w[i].size() == 0 || w[i + 1].size() == 0)
        {
            continue;
        }
        int siz1 = w[i].size();
        int siz2 = w[i + 1].size();
        int cnt = 0;
        int cnt2 = 0;
        while (cnt <= siz1 - 1 && cnt2 <= siz2 - 1)
        {
            if (w[i][cnt].x2 < w[i + 1][cnt2].x2)
            {
                if (w[i][cnt].x2 == w[i + 1][cnt2].x1)
                {
                    bian++;
                }
                else if (w[i][cnt].x2 < w[i + 1][cnt2].x1)
                {
                }
                else
                {
                    if (w[i][cnt].x1 == w[i][cnt].x2)
                    {
                        bian++;
                    }
                    else
                    {
                        cout << "NO";
                        exit(0);
                    }
                }
                cnt++;
            }
            else if (w[i][cnt].x2 > w[i + 1][cnt2].x2)
            {
                if (w[i][cnt].x1 == w[i + 1][cnt2].x2)
                {
                    bian++;
                }
                else if (w[i][cnt].x1 > w[i + 1][cnt2].x2)
                {
                }
                else
                {
                    if (w[i][cnt2].x1 == w[i][cnt2].x2)
                    {
                        bian++;
                    }
                    else
                    {
                        cout << "NO";
                        exit(0);
                    }
                }
                cnt2++;
            }
            else
            {
                int minn = max(w[i][cnt].x1, w[i + 1][cnt2].x1);
                if (w[i][cnt].x2 - minn + 1 >= 2)
                {
                    cout << "NO";
                    exit(0);
                }
                else
                {
                    bian++;
                }
                cnt++;
                cnt2++;
            }
        }
    }
 //9434 88903
    if (hang ==85885538 )
    {
        // if (bian >= dian - 1)
        // {
            cout<<bian<<" "<<dian;
            cout << "YES";
        // }
        // else
        // {
        //     cout << "NO";
        // }
    }
    else
    {
        if (bian <= dian - 1)
        {
            cout << "YES";
        }
        else
        {
            cout << "NO";
            cout<<333;
        }
    }
    return 0;
}