#define CPP17
#include <limits>
#include <initializer_list>
#include <utility>
#include <bitset>
#include <tuple>
#include <type_traits>
#include <functional>
#include <string>
#include <array>
#include <deque>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <iterator>
#include <algorithm>
#include <complex>
#include <random>
#include <numeric>
#include <iostream>
#include <iomanip>
#include <sstream>
#include <regex>
#include <cassert>
#include <cstddef>
#ifdef CPP17
#include <variant>
#endif

#define endl codeforces

#define ALL(v) std::begin(v), std::end(v)
#define ALLR(v) std::rbegin(v), std::rend(v)

using ll = std::int64_t;
using ull = std::uint64_t;
using pii = std::pair<int, int>;
using tii = std::tuple<int, int, int>;
using pll = std::pair<ll, ll>;
using tll = std::tuple<ll, ll, ll>;
using size_type = ssize_t;
template <typename T> using vec = std::vector<T>;
template <typename T> using vvec = vec<vec<T>>;

template <typename T> const T& var_min(const T &t) { return t; }
template <typename T> const T& var_max(const T &t) { return t; }
template <typename T, typename... Tail> const T& var_min(const T &t, const Tail&... tail) { return std::min(t, var_min(tail...)); }
template <typename T, typename... Tail> const T& var_max(const T &t, const Tail&... tail) { return std::max(t, var_max(tail...)); }
template <typename T, typename... Tail> void chmin(T &t, const Tail&... tail) { t = var_min(t, tail...); }
template <typename T, typename... Tail> void chmax(T &t, const Tail&... tail) { t = var_max(t, tail...); }

template <typename T, std::size_t Head, std::size_t... Tail> 
struct multi_dim_array { using type = std::array<typename multi_dim_array<T, Tail...>::type, Head>; };

template <typename T, std::size_t Head> 
struct multi_dim_array<T, Head> { using type = std::array<T, Head>; };

template <typename T, std::size_t... Args> using mdarray = typename multi_dim_array<T, Args...>::type;

#ifdef CPP17
template <typename T, typename F, typename... Args> 
void fill_seq(T &t, F f, Args... args) { 
    if constexpr (std::is_invocable<F, Args...>::value) { 
        t = f(args...); 
    } else { 
        for (size_type i = 0; i < t.size(); i++) fill_seq(t[i], f, args..., i); 
    } 
}
#endif

template <typename T> vec<T> make_v(size_type sz) { return vec<T>(sz); }

template <typename T, typename... Tail> 
auto make_v(size_type hs, Tail&&... ts) { 
    auto v = std::move(make_v<T>(std::forward<Tail>(ts)...)); 
    return vec<decltype(v)>(hs, v); 
}

namespace init__ { 
struct InitIO { 
    InitIO() { std::cin.tie(nullptr); std::ios_base::sync_with_stdio(false); std::cout << std::fixed << std::setprecision(30); } 
} init_io; 
}
#define CPP17


const size_type SIZE = 3010;
mdarray<ll, SIZE, SIZE, 4> dp;
mdarray<bool, SIZE, SIZE, 4> used;

int main() {
    ll r, c, k;
    std::cin >> r >> c >> k;
    auto grid = make_v<ll>(r, c);
    for (ll i = 0; i < k; i++) {
        ll a, b, c;
        std::cin >> a >> b >> c;
        grid[a - 1][b - 1] = c;
    }

    auto calc = [&](ll i, ll j, ll k) {
        auto rec = [&](ll i, ll j, ll k, auto f) -> ll {
            if (used[i][j][k]) return dp[i][j][k];
            used[i][j][k] = true;
            if (i == r - 1 && j == c - 1) return dp[i][j][k] = (k < 3 ? grid[i][j] : 0);
            ll maxv = 0;
            if (i + 1 < r) {
                chmax(maxv, f(i + 1, j, 0, f));
                if (k < 3) chmax(maxv, f(i + 1, j, 0, f) + grid[i][j]);
            }
            if (j + 1 < c) {
                chmax(maxv, f(i, j + 1, k, f));
                if (k < 3) chmax(maxv, f(i, j + 1, k + 1, f) + grid[i][j]);
            }
            return dp[i][j][k] = maxv;
        };
        return rec(i, j, k, rec);
    };

    std::cout << calc(0, 0, 0) << "\n";
    return 0;
}


Measured memory_bytes: 391808