#include<bits/stdc++.h>
using namespace std;

#define endl '\n'
#define lfs cout<<fixed<<setprecision(10)
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()
#define spa << " " <<
#define test cout<<"test"<<endl;
#define fi first
#define se second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define EB emplace_back
#define rep(i,n,m) for(ll i = (n); i < (ll)(m); i++)
#define rrep(i,n,m) for(ll i = (m) - 1; i >= (ll)(n); i--)
using ll = long long;
using ld = long double;
const ll MOD = 1e9+7;
//const ll MOD = 998244353;
const ll INF = 1e18;
using P = pair<ll, ll>;
template<typename T>
void chmin(T &a,T b){if(a>b)a=b;}
template<typename T>
void chmax(T &a,T b){if(a<b)a=b;}
void pmod(ll &a,ll b){a=(a+b)%MOD;}
void pmod(ll &a,ll b,ll c){a=(b+c)%MOD;}
void qmod(ll &a,ll b){a=(a*b)%MOD;}
void qmod(ll &a,ll b,ll c){a=(b*c)%MOD;}
ll median(ll a,ll b, ll c){return a+b+c-max({a,b,c})-min({a,b,c});}
void ans1(bool x){if(x) cout<<"Yes"<<endl;else cout<<"No"<<endl;}
void ans2(bool x){if(x) cout<<"YES"<<endl;else cout<<"NO"<<endl;}
void ans3(bool x){if(x) cout<<"Yay!"<<endl;else cout<<":("<<endl;}
template<typename T1,typename T2>
void ans(bool x,T1 y,T2 z){if(x)cout<<y<<endl;else cout<<z<<endl;}  
template<typename T>
void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++)
{cout<<v[i][0];for(ll j=1;j<w;j++)cout spa v[i][j];cout<<endl;}};
void debug(vector<string>&v,ll h,ll w){for(ll i=0;i<h;i++)
{for(ll j=0;j<w;j++)cout<<v[i][j];cout<<endl;}};
template<typename T>
void debug(vector<T>&v,ll n){if(n!=0)cout<<v[0];
for(ll i=1;i<n;i++)cout spa v[i];cout<<endl;};
template<typename T>
vector<vector<T>>vec(ll x, ll y, T w){
  vector<vector<T>>v(x,vector<T>(y,w));return v;}
ll gcd(ll x,ll y){ll r;while(y!=0&&(r=x%y)!=0){x=y;y=r;}return y==0?x:y;}
vector<ll>dx={1,0,-1,0,1,1,-1,-1};
vector<ll>dy={0,1,0,-1,1,-1,1,-1};
template<typename T>
vector<T> make_v(size_t a,T b){return vector<T>(a,b);}
template<typename... Ts>
auto make_v(size_t a,Ts... ts){
  return vector<decltype(make_v(ts...))>(a,make_v(ts...));
}
ostream &operator<<(ostream &os, pair<ll, ll>&p){
  return os << p.first << " " << p.second;
}  
struct UnionFind {
  vector<ll> data;
  vector<ll> difweight;
  UnionFind(ll size){
    data.assign(size,-1);
    difweight.assign(size,0);
  }
  bool unite(ll x, ll y, ll w) { //y=x+w
    w += weight(x); w -= weight(y);
    x = root(x); y = root(y);
    if (x != y) {
      if (data[y] < data[x]) swap(x, y), w = -w;
      data[x] += data[y]; 
      data[y] = x;
      difweight[y] = w;
    }
    return x != y;
  }
  bool find(ll x, ll y) {
    return root(x) == root(y);
  }
  ll diff(ll x,ll y){
    return weight(y)-weight(x);
  }
  ll weight(ll x){
    root(x);
    return difweight[x];
  }
  ll root(ll x) {
    if(data[x] < 0){
      return x;
    }
    else{
      ll tmp = root(data[x]);
      difweight[x] += difweight[data[x]];
      return data[x] = tmp;
    }
  }
  ll size(ll x) {
    return -data[root(x)];
  }
  ll debug(){
    rep(i,0,data.size()){
      root(i);
      cout<<i spa data[i] spa difweight[i] spa weight(i)<<endl;
    }
    cout<<endl;
  }
};
int main(){
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll res=0,buf=0;
  bool judge = true;
  ll h,w;cin>>h>>w;
  ll n;cin>>n;
  vector<vector<P>>v(h);
  rep(i,0,n){
    ll x,y,a;cin>>x>>y>>a;
    x--;y--;
    v[x].EB(y,a);
  }
  UnionFind uf(w);
  rep(i,0,h){
    sort(ALL(v[i]));
    rep(j,0,(ll)v[i].size()-1){
      auto x1=v[i][j],x2=v[i][j+1];
      if(uf.find(v[i][j].fi,v[i][j+1].fi)){
        if(uf.diff(x1.fi,x2.fi)!=x2.se-x1.se)judge=false;
      }
      else{
        uf.unite(x1.fi,x2.fi,x2.se-x1.se);
      }
    }
  }
  vector<ll>val(w,INF);
  rep(i,0,w){
    chmin(val[uf.root(i)],uf.weight(i));
  }
  rep(i,0,h){
    for(auto z:v[i]){
      if(z.se<uf.weight(z.fi)-val[uf.root(z.fi)])judge=false;
    }
  }
  ans1(judge);
  return 0;
}

Measured memory_bytes: 8064