// >>> TEMPLATES
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
#define int ll
#define double ld
#define rep(i,n) for (int i = 0; i < (int)(n); i++)
#define rep1(i,n) for (int i = 1; i <= (int)(n); i++)
#define repR(i,n) for (int i = (int)(n)-1; i >= 0; i--)
#define rep1R(i,n) for (int i = (int)(n); i >= 1; i--)
#define loop(i,a,B) for (int i = a; i B; i++)
#define loopR(i,a,B) for (int i = a; i B; i--)
#define all(x) (x).begin(), (x).end()
#define allR(x) (x).rbegin(), (x).rend()
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define fst first
#define snd second
#define INF (numeric_limits<int>::max()/2-1)
#ifdef LOCAL
#include "debug.hpp"
#define dump(...) cerr << "[" << __LINE__ << ":" << __FUNCTION__ << "] ", dump_impl(#__VA_ARGS__, __VA_ARGS__)
#define say(x) cerr << "[" << __LINE__ << ":" << __FUNCTION__ << "] " << x << endl
#define debug if (1)
#else
#define dump(...) (void)(0)
#define say(x) (void)(0)
#define debug if (0)
#endif
template <class T> using pque_max = priority_queue<T>;
template <class T> using pque_min = priority_queue<T, vector<T>, greater<T> >;
template <class T, class = typename T::iterator, class = typename enable_if<!is_same<T, string>::value>::type>
ostream& operator<<(ostream& os, T const& v) { bool f = true; for (auto const& x : v) os << (f ? "" : " ") << x, f = false; return os; }
template <class T, class = typename T::iterator, class = typename enable_if<!is_same<T, string>::value>::type>
istream& operator>>(istream& is, T &v) { for (auto& x : v) is >> x; return is; }
template <class T, class S> istream& operator>>(istream& is, pair<T,S>& p) { return is >> p.first >> p.second; }
struct IOSetup { IOSetup() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); } } iosetup;
template <class F> struct FixPoint : private F {
    constexpr FixPoint(F&& f) : F(forward<F>(f)) {}
    template <class... T> constexpr auto operator()(T&&... x) const { return F::operator()(*this, forward<T>(x)...); }
};
struct MakeFixPoint {
    template <class F> constexpr auto operator|(F&& f) const { return FixPoint<F>(forward<F>(f)); }
};
#define MFP MakeFixPoint()|
#define def(name, ...) auto name = MFP [&](auto &&name, __VA_ARGS__)
template <class T, size_t d> struct vec_impl {
    using type = vector<typename vec_impl<T,d-1>::type>;
    template <class... U> static type make_v(size_t n, U&&... x) { return type(n, vec_impl<T,d-1>::make_v(forward<U>(x)...)); }
};
template <class T> struct vec_impl<T,0> { using type = T; static type make_v(T const& x = {}) { return x; } };
template <class T, size_t d = 1> using vec = typename vec_impl<T,d>::type;
template <class T, size_t d = 1, class... Args> auto make_v(Args&&... args) { return vec_impl<T,d>::make_v(forward<Args>(args)...); }
template <class T> void quit(T const& x) { cout << x << endl; exit(0); }
template <class T> constexpr bool chmin(T& x, T const& y) { if (x > y) { x = y; return true; } return false; }
template <class T> constexpr bool chmax(T& x, T const& y) { if (x < y) { x = y; return true; } return false; }
template <class It> constexpr auto sumof(It b, It e) { return accumulate(b,e,typename iterator_traits<It>::value_type{}); }
template <class T> int sz(T const& x) { return x.size(); }
// <<<
// >>> segment tree
template <class Handler>
struct Segtree : Handler {
    using Value = typename Handler::Value;
    using Handler::unit; // () -> Value
    using Handler::merge; // (Value,Value) -> Value

    vector<Value> v; // use v[1..2*cap-1]
    int cap; // capacity: power of 2
    int n; // original size

    Segtree() {}
    Segtree(int n) { init(n); }
    template <class It> Segtree(It first, It last) { init(first, last); }
    void init(int n) {
        assert(n >= 0); this->n = n;
        for (cap = 1; cap < n; cap <<= 1) ;;
		v.assign(2*cap, unit());
    }
    template <class It> void init(It first, It last) {
        init(distance(first,last));
        copy(first, last, next(v.begin(), cap));
        for (int i = cap-1; i >= 1; i--) v[i] = merge(v[2*i],v[2*i+1]);
    }
    int size() const { return n; }
    void set(int i, Value const& x) {
        assert(0 <= i && i < size());
        i += cap; v[i] = x;
        while (i > 1) i >>= 1, v[i] = merge(v[2*i],v[2*i+1]);
    }
    Value operator[](int i) const { return get(i); }
    Value get(int i) const {
        assert(0 <= i && i < size());
        return v[cap + i];
    }
    // [l,r)
    Value get(int l, int r) const {
        assert(0 <= l && l <= r && r <= size());
        Value x = unit(), y = unit();
        for (l += cap, r += cap; l < r; l >>= 1, r >>= 1) {
            if (l&1) x = merge(x, v[l++]);
            if (r&1) y = merge(v[--r], y);
        }
        return merge(x,y);
    }
    vector<Value> dat() const {
        vector<Value> ret(size());
        for (int i = 0; i < size(); i++) ret[i] = get(i);
        return ret;
    }
};
// <<<
struct RangeMax {
    using Value = int;
    constexpr static Value unit() { return 0; }
    constexpr static Value merge(Value x, Value y) { return max(x,y); }
};
// >>> coordinate compression

template <class T>
struct Compress {
    vector<T> v;
    bool ok = false;
    void add(T const& x) { ok = false; v.push_back(x); }
    template <class It>
    void add(It f, It l) { ok = false; copy(f,l,back_inserter(v)); }
    void init() { sort(all(v)); v.erase(unique(all(v)), v.end()); ok = true; }
    int size() const { return v.size(); }
    T operator[](int i) const { assert(ok); return v[i]; }
    int find(T const& x) const {
        assert(ok); auto it = lower_bound(all(v),x);
        //assert(*it == x);
        return it-v.begin();
    }
};

// <<<

int32_t main() {
    int H,W,q; cin >> W >> H >> q;
    vector<int> x(q),y(q),L(q);
    Compress<int> Z;
    Z.add(0), Z.add(W), Z.add(H);
    rep (i,q) cin >> x[i] >> y[i] >> L[i], Z.add(x[i]), Z.add(y[i]);
    Z.init();
    dump(Z.v);
    rep (i,q) x[i] = Z.find(x[i]), y[i] = Z.find(y[i]);

    int n = Z.size();
    Segtree<RangeMax> seg_u(n), seg_d(n), seg_l(n), seg_r(n);

    auto fl = [&](auto &seg, int L, int val) -> int {
        dump(L,val);
        dump(seg.dat());
        if (seg.get(0,L) < val) return n;
        int l = 0, r = L;
        while (l+1 < r) {
            int m = (l+r)/2;
            (seg.get(0,m) < val ? l : r) = m;
        }
        dump(l,r);
        assert(seg.get(0,l) < val);
        assert(seg.get(l) >= val);
        return l;
    };
    auto fr = [&](auto &seg, int L, int val) -> int {
        dump(L,val);
        dump(seg.dat());
        if (seg.get(L,n) < val) return -1;
        int l = L, r = n;
        while (l+1 < r) {
            int m = (l+r)/2;
            (seg.get(m,n) < val ? r : l) = m;
        }
        dump(l,r);
        assert(seg.get(l+1,n) < val);
        assert(seg.get(l) >= val);
        return l;
    };
    rep (i,q) {
        if (Z[x[i]] == 0) {
            say("Z[x[i]] == 0");
            int xx = 1+min(H,seg_u.get(y[i])+L[i]);
            int il = fl(seg_l, Z.find(xx), Z[y[i]]);
            int ir = fl(seg_r, Z.find(xx), W+1-Z[y[i]]);
            dump(xx,il,ir);
            if (il < ir) {
                seg_u.set(y[i],0);
                seg_l.set(il,0);
            } else if (il > ir) {
                seg_u.set(y[i],0);
                seg_r.set(ir,0);
            } else {
                assert(il == n);
                if (seg_u.get(y[i])+L[i]+seg_d.get(y[i]) > H) {
                    seg_u.set(y[i],0);
                    seg_d.set(y[i],0);
                } else {
                    seg_u.set(y[i], seg_u.get(y[i])+L[i]);
                }
            }
        } else if (Z[y[i]] == 0) {
            say("Z[y[i]] == 0");
            int yy = 1+min(W,seg_l.get(x[i])+L[i]);
            int iu = fl(seg_u, Z.find(yy), Z[x[i]]);
            int id = fl(seg_d, Z.find(yy), H+1-Z[x[i]]);
            dump(yy,iu,id);
            if (iu < id) {
                seg_l.set(x[i],0);
                seg_u.set(iu,0);
            } else if (iu > id) {
                seg_l.set(x[i],0);
                seg_d.set(id,0);
            } else {
                assert(iu == n);
                if (seg_l.get(x[i])+L[i]+seg_r.get(x[i]) > W) {
                    seg_l.set(x[i],0);
                    seg_r.set(x[i],0);
                } else {
                    seg_l.set(x[i], seg_l.get(x[i])+L[i]);
                }
            }
        } else if (Z[x[i]] == H+1) {
            say("Z[x[i]] == H+1");
            int xx = 1+H-min(H,seg_d.get(y[i])+L[i]);
            int il = fr(seg_l, Z.find(xx), Z[y[i]]);
            int ir = fr(seg_r, Z.find(xx), W+1-Z[y[i]]);
            dump(xx,il,ir);
            if (il < ir) {
                seg_d.set(y[i],0);
                seg_r.set(ir,0);
            } else if (il > ir) {
                seg_d.set(y[i],0);
                seg_l.set(il,0);
            } else {
                assert(il == -1);
                if (seg_u.get(y[i])+L[i]+seg_d.get(y[i]) > H) {
                    seg_u.set(y[i],0);
                    seg_d.set(y[i],0);
                } else {
                    seg_d.set(y[i], L[i]+seg_d.get(y[i]));
                }
            }
        } else if (Z[y[i]] == W+1) {
            say("Z[y[i]] == W+1");
            int yy = 1+W-min(W,seg_r.get(x[i])+L[i]);
            int iu = fr(seg_u, Z.find(yy), Z[x[i]]);
            int id = fr(seg_d, Z.find(yy), H+1-Z[x[i]]);
            dump(yy,iu,id);
            if (iu < id) {
                seg_r.set(x[i],0);
                seg_d.set(id,0);
            } else if (iu > id) {
                seg_r.set(x[i],0);
                seg_u.set(iu,0);
            } else {
                assert(iu == -1);
                if (seg_l.get(x[i])+L[i]+seg_r.get(x[i]) > W) {
                    seg_l.set(x[i],0);
                    seg_r.set(x[i],0);
                } else {
                    seg_r.set(x[i], L[i]+seg_r.get(x[i]));
                }
            }
        } else {
            assert(0);
        }
    }

    int sum = 0;
    rep (i,n) sum += seg_u.get(i);
    rep (i,n) sum += seg_d.get(i);
    rep (i,n) sum += seg_l.get(i);
    rep (i,n) sum += seg_r.get(i);

    cout << sum << endl;

}