#include <bits/stdc++.h>

using namespace std;

using int64 = long long;
const int mod = 1e9 + 7;

const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;


template< typename T1, typename T2 >
ostream &operator<<(ostream &os, const pair< T1, T2 > &p) {
  os << p.first << " " << p.second;
  return os;
}

template< typename T1, typename T2 >
istream &operator>>(istream &is, pair< T1, T2 > &p) {
  is >> p.first >> p.second;
  return is;
}

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
vector< T > make_v(size_t a) {
  return vector< T >(a);
}

template< typename T, typename... Ts >
auto make_v(size_t a, Ts... ts) {
  return vector< decltype(make_v< T >(ts...)) >(a, make_v< T >(ts...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}

template< typename F >
struct FixPoint : F {
  FixPoint(F &&f) : F(forward< F >(f)) {}

  template< typename... Args >
  decltype(auto) operator()(Args &&... args) const {
    return F::operator()(*this, forward< Args >(args)...);
  }
};

template< typename F >
inline decltype(auto) MFP(F &&f) {
  return FixPoint< F >{forward< F >(f)};
}


int main() {
  int W, H, N;
  cin >> W >> H >> N;
  vector< int > X(N), Y(N), L(N);

  for(int i = 0; i < N; i++) {
    cin >> X[i] >> Y[i] >> L[i];
  }


  map< int, int > mpSita, mpUe;
  map< int, int > mpMigi, mpHidari;


  for(int i = 0; i < N; i++) {
    if(Y[i] == 0) {

      mpSita[X[i]] += L[i];

      int cash = mpSita[X[i]];

      int64 times = infll;
      int type = -1;

      if(mpUe.count(X[i])) {
        if(mpUe[X[i]] <= cash) {
          if(chmin(times, mpUe[X[i]])) type = 0;
        }
      }

      for(auto &p : mpHidari) {
        if(p.first <= cash) {
          if(p.second >= X[i]) {
            if(chmin(times, p.first)) type = 1;
          }
        }
      }

      for(auto &p : mpMigi) {
        if(p.first <= cash) {
          if(p.second <= X[i]) {
            if(chmin(times, p.first)) type = 2;
          }
        }
      }

      if(H + 1 <= cash) {
        if(chmin(times, H + 1)) type = 3;
      }

      if(~type) {
        mpSita.erase(X[i]);
        if(type == 0) {
          mpUe.erase(X[i]);
        } else if(type == 1) {
          mpHidari.erase(times);
        } else if(type == 2) {
          mpMigi.erase(times);
        }
      }

    } else if(Y[i] == H + 1) {

      if(!mpUe.count(X[i])) mpUe[X[i]] = H + 1;
      mpUe[X[i]] -= L[i];

      int cash = mpUe[X[i]];

      int64 times = -infll;
      int type = -1;

      if(mpSita.count(X[i])) {
        if(mpSita[X[i]] >= cash) {
          if(chmax(times, mpSita[X[i]])) type = 0;
        }
      }

      for(auto &p : mpHidari) {
        if(p.first >= cash) {
          if(p.second >= X[i]) {
            if(chmax(times, p.first)) type = 1;
          }
        }
      }

      for(auto &p : mpMigi) {
        if(p.first >= cash) {
          if(p.second <= X[i]) {
            if(chmax(times, p.first)) type = 2;
          }
        }
      }

      if(cash <= 0) {
        if(chmax(times, 0)) type = 3;
      }

      if(~type) {
        mpUe.erase(X[i]);
        if(type == 0) {
          mpSita.erase(X[i]);
        } else if(type == 1) {
          mpHidari.erase(times);
        } else if(type == 2) {
          mpMigi.erase(times);
        }
      }


    } else if(X[i] == 0) {

      mpHidari[Y[i]] += L[i];

      int cash = mpHidari[Y[i]];

      int64 times = infll;
      int type = -1;

      if(mpMigi.count(Y[i])) {
        if(mpMigi[Y[i]] <= cash) {
          if(chmin(times, mpMigi[Y[i]])) type = 0;
        }
      }

      for(auto &p : mpUe) {
        if(p.first <= cash) {
          if(p.second <= Y[i]) {
            if(chmin(times, p.first)) type = 1;
          }
        }
      }

      for(auto &p : mpSita) {
        if(p.first <= cash) {
          if(p.second >= Y[i]) {
            if(chmin(times, p.first)) type = 2;
          }
        }
      }

      if(W + 1 <= cash) {
        if(chmin(times, W + 1)) type = 3;
      }


      if(~type) {
        mpHidari.erase(Y[i]);
        if(type == 0) {
          mpMigi.erase(Y[i]);
        } else if(type == 1) {
          mpUe.erase(times);
        } else if(type == 2) {
          mpSita.erase(times);
        }
      }


    } else if(X[i] == W + 1) {


      if(!mpMigi.count(Y[i])) mpMigi[Y[i]] = W + 1;
      mpMigi[Y[i]] -= L[i];

      int cash = mpMigi[Y[i]];


      int64 times = -infll;
      int type = -1;

      if(mpHidari.count(Y[i])) {
        if(mpHidari[Y[i]] >= cash) {
          if(chmax(times, mpHidari[Y[i]])) type = 0;
        }
      }

      for(auto &p : mpUe) {
        if(p.first >= cash) {
          if(p.second <= Y[i]) {
            if(chmax(times, p.first)) type = 1;
          }
        }
      }

      for(auto &p : mpSita) {
        if(p.first >= cash) {
          if(p.second >= Y[i]) {
            if(chmax(times, p.first)) type = 2;
          }
        }
      }

      if(cash <= 0) {
        if(chmax(times, 0)) type = 3;
      }

      if(~type) {
        mpMigi.erase(Y[i]);
        if(type == 0) {
          mpHidari.erase(Y[i]);
        } else if(type == 1) {
          mpUe.erase(times);
        } else if(type == 2) {
          mpSita.erase(times);
        }
      }

    } else {
      assert(0);
    }
  }

  int64 ret = 0;
  for(auto &p : mpUe) ret += H + 1 - p.second;
  for(auto &p : mpMigi) ret += W + 1 - p.second;
  for(auto &p : mpHidari) ret += p.second;
  for(auto &p : mpSita) ret += p.second;
  cout << ret << endl;


}