#include <bits/stdc++.h>
#include <random>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef double ld;
//#define ll __int128
//#define int ll
//#define char ll
//#define double ld
typedef vector<char> vc;
typedef vector<vc> vvc;
typedef vector<vvc> vvvc;
typedef pair<int, int> pii;
typedef pair<pii, pii> piii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<pii> vpi;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;
typedef vector<short> vs;
typedef vector<vs> vvs;
typedef vector<vvs> vvvs;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;
typedef vector<ld> vld;
typedef vector<vld> vvld;
typedef vector<vvld> vvvld;
typedef vector<string> vst;
typedef vector<vst> vvst;
typedef pair<ld, ld> pld;

#define inmin(a, b) a = min(a, (b))
#define inmax(a, b) a = max(a, (b))
#define ALL(a) a.begin(),a.end()
#define RALL(a) a.rbegin(),a.rend()
#define sqr(x) ((x) * (x))
#define fori(i, n) for(int i = 0; i < int(n); ++i)
#define SZ(a) ((int)((a).size()))
#define triple(T) tuple<T, T, T>
#define quad(T) tuple<T, T, T, T>
#define watch(x) cerr << (#x) << " = " << (x) << endl;

#ifdef MAX_HOME
#define cerr cout
#else
#define cerr if (false) cerr
#endif

const double PI = 2 * acos(0.0);
#define rand shittttty_shit
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
mt19937_64 rng_64(chrono::steady_clock::now().time_since_epoch().count());

const string DIGITS = "0123456789";
const string ALPH = "abcdefghijklmnopqrstuvwxyz";


template<class T0, class T1>
inline ostream &operator<<(ostream &out, pair<T0, T1> &a) {
    return out << "{" << a.first << ", " << a.second << "}";
}

template<class T0, class T1>
inline istream &operator>>(istream &in, pair<T0, T1> &a) {
    return in >> a.first >> a.second;
}

template<class T0, class T1, class T2>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << "}";
}

template<class T0, class T1, class T2, class T3>
inline ostream &operator<<(ostream &out, tuple<T0, T1, T2, T3> &a) {
    return out << "{" << get<0>(a) << ", " << get<1>(a) << ", " << get<2>(a) << ", " << get<3>(a) << "}";
}

template<class T>
inline ostream &operator<<(ostream &out, vector<T> &a) {
    out << "[";
    fori (i, a.size())out << a[i] << vector<string>{", ", "]  "}[i + 1 == a.size()];
    return out;
}


void smain();


signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
#ifdef MAX_HOME
    freopen("input.txt", "r", stdin);
    clock_t start = clock();
#endif
#ifdef HK_CUP
    freopen("finput.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    cout << setprecision(12) << fixed;
    smain();
#ifdef MAX_HOME
#ifndef HK_CUP
    cout << "\n\nTOTAL EXECUTION TIME: " << float(clock() - start) / CLOCKS_PER_SEC << endl;
#endif
#endif
    return 0;
}

const int N = 1e5 + 10;

void out_and_exit(bool ans) {
    cout << (ans ? "Yes\n" : "No\n");
    exit(0);
}

struct DSU {
    int parent[N];
    int dif[N];
    vi verts[N];

    DSU() {
        fill(parent, parent + N, -1);
    }

    bool have_set(int v) {
        return parent[v] != -1;
    }

    void make_set(int v) {
        parent[v] = v;
        dif[v] = 0;
        verts[v] = {v};
    }

    int find_set(int v) {
        return parent[v] == v ? v : parent[v] = find_set(parent[v]);
    }

    void union_sets(int u, int v, int df) { // df = f[v] - f[u];
        int fu = find_set(u);
        int fv = find_set(v);
        if (fu == fv) {
            if (dif[v] - dif[u] != df) {
                out_and_exit(false);
            }
            return;
        }
        if (verts[fu].size() < verts[fv].size()) {
            swap(fu, fv);
            swap(u, v);
            df *= -1;
        }
        parent[fv] = fu;
        int inc = dif[u] - dif[v] + df;
        for (auto cur : verts[fv]) {
            dif[cur] += inc;
        }
        verts[fu].insert(verts[fu].end(), ALL(verts[fv]));

    }
};

vector<pii> g[N];
vi not_empty;



void smain() {
    int dum, n;
    cin >> dum >> dum >> n;
    fori (_, n) {
        int x, y, a;
        cin >> x >> y >> a;
        g[x].push_back({y, a});
    }
    fori (x, N) {
        sort(ALL(g[x]));
        if (!g[x].empty())
            not_empty.push_back(x);
    }
    DSU dsu;
    for (auto x : not_empty) {
        for (auto py : g[x]) {
            int y = py.first;
            int val = py.second;
            if (!dsu.have_set(y)) {
                dsu.make_set(y);
            }
            dsu.union_sets(y, g[x][0].first, g[x][0].second - val);
        }
    }
    vi min_val(N, 0);
    fori (i, N) {
        if (dsu.have_set(i)) {
            for (auto cur : dsu.verts[i]) {
                inmax(min_val[i], -dsu.dif[cur]);
            }
        }
    }
    for (auto x : not_empty) {
        for (auto py : g[x]) {
            int y = py.first;
            int val = py.second;
            int pivot_val = val - dsu.dif[y];
            if (pivot_val < min_val[dsu.find_set(y)]) {
                out_and_exit(false);
            }
        }
    }
    out_and_exit(true);
}

Measured memory_bytes: 15760