#include<bits/stdc++.h>
using namespace std;
const int N=200005;
int n,m,k;
vector<pair<int,int>>wall[N],seg[N];
vector<int>col[N];
int fa[N];
int getf(int v)
{
    if(v==fa[v]) return v;
    else return fa[v]=getf(fa[v]);
}
void merge(int u,int v)
{
    int fu=getf(u),fv=getf(v);
    if(fu!=fv) fa[fu]=fv;
    return;
}
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr),cout.tie(nullptr);
    cin>>n>>m>>k;
    for(int i=1;i<=k;i++)
    {
        int x1,x2,y;
        cin>>x1>>x2>>y;
        wall[y].emplace_back(x1,x2);
    }
    if(n==1)
    {
        cout<<"YES";
        return 0;
    }
    if(m>2*k+1)
    {
        cout<<"NO";
        return 0;
    }
    for(int i=1;i<=m;i++)
        if(!wall[i].empty())
        {
            sort(wall[i].begin(),wall[i].end());
            if(1<=wall[i].front().first-1) seg[i].emplace_back(1,wall[i].front().first-1);
            for(int j=1;j<(int)wall[i].size();j++)
                if(wall[i][j-1].second+1<=wall[i][j].first-1) seg[i].emplace_back(wall[i][j-1].second+1,wall[i][j].first-1);
            if(wall[i].back().second+1<=n) seg[i].emplace_back(wall[i].back().second+1,n);
        }
        else seg[i].emplace_back(1,n);
    int tot=0;
    for(int i=1;i<=m;i++)
    {
        col[i].resize(seg[i].size()); 
//        cerr<<"start"<<i<<"\n";
        for(int j=0;j<(int)seg[i].size();j++)
        {
            auto [l,r]=seg[i][j];
            int p=lower_bound(seg[i-1].begin(),seg[i-1].end(),make_pair(l+1,0))-seg[i-1].begin()-1;
            int q=lower_bound(seg[i-1].begin(),seg[i-1].end(),make_pair(r+1,0))-seg[i-1].begin()-1;
//            assert(p>=0&&q>=0);
//            cerr<<"now"<<l<<" "<<r<<"\n";
            if(p>=0&&p<=q)
            {
//                cerr<<"merge\n";
                vector<int>pos;
                for(int k=p;k<=q;k++)
                {
                    auto [ll,lr]=seg[i-1][k];
                    int len=min(r,lr)-max(ll,l)+1;
                    if(len>1)
                    {
                        cout<<"NO";
                        return 0;
                    }
                    assert(len==1);
                    pos.emplace_back(getf(col[i-1][k]));
                }
                sort(pos.begin(),pos.end());
                for(int k=1;k<(int)pos.size();k++)
                    if(pos[k]==pos[k-1])
                    {
                        cout<<"NO";
                        return 0;
                    }
                for(int k=1;k<(int)pos.size();k++)
                    merge(pos[k],pos[k-1]);
            }
            else tot++,fa[tot]=tot,col[i][j]=tot;
        }
    }
    cout<<"YES";
    return 0;
}