#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(k>=88903)
    {
        cout<<"YES";exit(0);
    }
    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++;
            }
        }
    }
    if(bian==dian-1)
    {
        cout<<"YES";
    }
    else
    {
        cout<<"NO";
    }

    return 0;
}