#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int,int> PII;
typedef pair<ll,ll> PLL;
#define endl '\n'
#define debug(x) cout<<#x<<": "<<x<<endl
#define lowbit(x) (x&-x)
#define gcd __gcd
#define i128 __int128
#define rep(i, a, b) for(ll i = (a); i <= (b); i++)
#define per(i, a, b) for(ll i = (a); i >= (b); i--)
const int N=2e5+10,M=1e3+10;
const ll mod=1e9+7;
const ld eps=1e-12;
const double pi=acos(-1.0);
const double pi1=pi/180,pi2=180/pi;
mt19937_64 rnd(chrono::steady_clock::now().time_since_epoch().count());
//unordered_map<int,int>mp;
#define poly vector<int>

void solve()
{
    ll n,m,k;
    cin>>n>>m>>k;
    ll num_v=n*m;
    ll num_e=(m-1)*n+(n-1)*m;
    map<ll,vector<PLL>>path;
    while(k--)
    {
        ll x1,x2,y;
        cin>>x1>>x2>>y;
        path[y].push_back({x1,x2});
    }
    ll last_y=0;
    vector<PLL>last_q;
    last_q.push_back({1,n});
    for(auto [y,q]:path)
    {
        ll last_ed=0;
        sort(q.begin(),q.end());
        for(auto [st,ed]:q)
        {
            num_v-=ed-st+1;
            num_e-=ed-st+1;
            num_e-=ed-st;
            if(y!=m) num_e-=ed-st+1; 
            if(last_ed!=st-1) num_e--;
            if(ed!=n) num_e--;
            last_ed=ed;
        }
        if(y==last_y+1)
        {
            ll len1=last_q.size(),len2=q.size();
            ll p1=0,p2=0;
            while(p1<len1&&p2<len1)
            {
                auto [st1,ed1]=last_q[p1];
                auto [st2,ed2]=q[p2];
                ll l=max(st1,st2),r=min(ed1,ed2);
                num_e+=max(0ll,r-l+1);
                if(ed1<=ed2) p1++;
                else p2++;
            }
        }
        last_y=y;
        last_q=q;
    }
    if(num_e!=num_v&&num_e!=num_v-1) while(1);
    if(num_e==num_v-1) cout<<"YES"<<endl;
    else cout<<"NO"<<endl;
}

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

	int T=1;
	//cin>>T;

	while(T--)
	{
		solve();
	}
	return 0;
}