#include <bits/stdc++.h>

#define rep(i, n) for (int i = 0; i < (n); i++)
#define repr(i, n) for (int i = (n) - 1; i >= 0; i--)

using namespace std;
using ll = long long;

const int INF = 1.01e9;

struct Kitune {
  int N;
  vector<int> dat;

  Kitune(int n) {
    N = 1;
    while (N < n) N *= 2;
    dat.resize(N * 2, -INF);
  }

  void update(int k, int v) {
    k += N;
    dat[k] = v;
    while (k > 1) {
      k >>= 1;
      dat[k] = max(dat[k * 2], dat[k * 2 + 1]);
    }
  }

  int query(int l, int r) {
    l += N;
    r += N;
    int res = -INF;
    while (l <= r) {
      if ((l & 1) == 1) res = max(res, dat[l++]);
      if ((r & 1) == 0) res = max(res, dat[r--]);
      l >>= 1;
      r >>= 1;
    }
    return res;
  }
};

vector<int> uniq(vector<int> a) {
  sort(a.begin(), a.end());
  a.erase(unique(a.begin(), a.end()), a.end());
  return a;
}

int doko(const vector<int> &a, int x) {
  return lower_bound(a.begin(), a.end(), x) - a.begin();
}

template<class T1, class T2, class T3>
ostream &operator<<(ostream &o, tuple<T1, T2, T3> t) {
  return o << '(' << get<0>(t) << ',' << get<1>(t) << ','<< get<2>(t) << ')';
}

int main() {
  int H, W, Q;
  cin >> H >> W >> Q;
  vector<int> X(Q), Y(Q), Z(Q);
  vector<vector<int>> zisyo{{0, H + 1}, {0, W + 1}};
  rep(i, Q) {
    cin >> X[i] >> Y[i] >> Z[i];
    zisyo[0].push_back(Y[i]);
    zisyo[0].push_back(H + 1 - Y[i]);
    zisyo[1].push_back(X[i]);
    zisyo[1].push_back(W + 1 - X[i]);
  }
  zisyo[0] = uniq(zisyo[0]);
  zisyo[1] = uniq(zisyo[1]);
  zisyo.emplace_back();
  zisyo.emplace_back();
  for (int x : zisyo[0]) zisyo[2].push_back(H + 1 - x);
  for (int x : zisyo[1]) zisyo[3].push_back(W + 1 - x);
  reverse(zisyo[2].begin(), zisyo[2].end());
  reverse(zisyo[3].begin(), zisyo[3].end());
  vector<Kitune> ktn;
  vector<vector<ll>> nagasa;
  rep(i, 4) ktn.emplace_back(zisyo[i].size());
  rep(i, 4) nagasa.emplace_back(zisyo[i].size());
  rep(i, Q) {
    int k, z;
    if (X[i] == 0) { k = 0; z = Y[i]; }
    else if (Y[i] == 0) { k = 1; z = W + 1 - X[i]; }
    else if (X[i] == W + 1) { k = 2; z = H + 1 - Y[i]; } 
    else if (Y[i] == H + 1) { k = 3; z = X[i]; }
    else abort();
    auto hidarite = [&]() -> tuple<int, int, int> {
      int butukaru = 0;
      int butukaranai = zisyo[(k + 1) % 4].size() - 1;
      while (butukaranai - butukaru > 1) {
        int aida = (butukaru + butukaranai) / 2;
        if (ktn[(k + 1) % 4].query(aida, zisyo[(k + 1) % 4].size() - 1) >= z) {
          butukaru = aida;
        } else {
          butukaranai = aida;
        }
      }
      return {zisyo[(k + 1) % 4].back() - zisyo[(k + 1) % 4][butukaru], 1, butukaru};
    };
    auto migite = [&]() -> tuple<int, int, int> {
      int butukaru = zisyo[(k + 3) % 4].size() - 1;
      int butukaranai = 0;
      while (butukaru - butukaranai > 1) {
        int aida = (butukaru + butukaranai) / 2;
        if (ktn[(k + 3) % 4].query(0, aida) >= zisyo[k].back() - z) {
          butukaru = aida;
        } else {
          butukaranai = aida;
        }
      }
      return {zisyo[(k + 3) % 4][butukaru], 3, butukaru};
    };
    auto mukai = [&]() -> tuple<int, int, int> {
      int s = doko(zisyo[(k + 2) % 4], zisyo[k].back() - z);
      return {zisyo[(k + 1) % 4].back() - nagasa[(k + 2) % 4][s], 2, s};
    };
    auto hazime_ni_butukaru = min({hidarite(), migite(), mukai()});
    int zi = doko(zisyo[k % 2], z);
    auto kakikae = [&](int k, int z, int v) {
      k %= 4;
      nagasa[k][z] = v;
      ktn[k].update(z, v);
    };
    kakikae(k, zi, nagasa[k][zi] + Z[i]);
    if (nagasa[k][zi] >= get<0>(hazime_ni_butukaru)) {
      kakikae(k, zi, 0);
      kakikae(k + get<1>(hazime_ni_butukaru), get<2>(hazime_ni_butukaru), 0);
    }
  }
  ll ans = 0;
  rep(i, 4) for (int x : nagasa[i]) ans += x;
  cout << ans << endl;
}