#include <algorithm>
#include <assert.h>
#include <bitset>
#include <cmath>
#include <functional>
#include <iostream>
#include <map>
#include <numeric>
#include <optional>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>

using namespace std;
using lint = long long;
using P = pair<int, int>;

#define rep(i, n) for (lint i = 0; i < (n); ++i)
#define rep1(i, n) for (lint i = 1; i < (n); ++i)
#define repn(i, a, b) for(lint i = (a); i < (b); ++i)
#define rep_inv(i, n) for (lint i = (n); i >= 0; --i)
#define all(vec) vec.begin(), vec.end()
#define cend printf("\n")

//constexpr lint mod = 998'244'353LL;
constexpr lint Mod = 1000'000'007LL;
constexpr lint Inf = 4'500'000'000'000'000'007LL; //4.5e18+7
constexpr double Pi = 3.141592653589793;

template<class T> using prique     = priority_queue<T>;
template<class T> using prique_inv = priority_queue<T, vector<T>, greater<T>>;
template<class T> bool chmin(T& a, const T& b) {
	if (a > b) {
		a = b; return true;
	}
	return false;
}
template<class T> bool chmax(T& a, const T& b) {
	if (a < b) {
		a = b; return true;
	}
	return false;
}
template<class T, class U>inline istream& operator>>(istream& is, pair<T, U>& rhs) { return is >> rhs.first >> rhs.second; }
template<class T, class U>inline ostream& operator<<(ostream& os, const pair<T, U>& rhs) { return os << "(" << rhs.first << ", " << rhs.second << ")"; }
template<class InputIterator> void arrin(InputIterator first, InputIterator last) { for (; first != last; ++first) cin >> (*first); }
template<class InputIterator> void arrout(InputIterator first, InputIterator last) {
	for (; first != last; ++first) {
		cout << (*first) << ((first + 1) != last ? " " : "\n");
	}
}

template<class T, class U> void print(const T& a, const U& b, bool f) {
	if (f) cout << a << "\n";
	else cout << b << "\n";
}

bool pri(lint x) { 
	for (lint i = 2; i * i <= x; ++i) {
		if (x % i == 0) return false;
	}
	return 1 < x; 
}

lint fact[3000000];
void fact_init(lint n, lint m = Mod) {
	if (3000000 <= n) return;
	fact[0] = fact[1] = 1;
	for (lint i = 2; i <= n; ++i) {
		fact[i] = i * fact[i - 1] % m;
	}
}

lint modpow(lint x, lint n, lint m = Mod) {
	lint res = 1;
	while (n > 0) {
		if (n & 1) res = res * x % m;
		x = x * x % m;
		n >>= 1;
	}
	return res;
}

lint intpow(lint x, lint n) {
	lint res = 1;
	while (n > 0) {
		if (n & 1) res *= x;
		x *= x;
		n >>= 1;
	}
	return res;
}

lint comb(lint n, lint r, lint m = Mod) {
	if (r == 0 || r == n) return 1;
	lint res = fact[n] * modpow(fact[n - r], m - 2, m) % m * modpow(fact[r], m - 2, m) % m;
	return res < 0 ? res + m : res;
}

map<lint, lint> factring(lint n) {
	map<lint, lint> res;
	for (lint i = 2; i * i <= n; ++i) {
		while (n % i == 0) {
			n /= i;
			++res[i];
		}
	}
	if (n != 1) ++res[n];
	return res;
}

int r, c, k;
lint v[3030][3030];
lint dp[3030][3030][4];
int main() {
	cin >> r >> c >> k;
	rep(i, k) {
		int x, y, v1;
		cin >> x >> y >> v1;
		x--; y--;
		v[x][y] = v1;
	}

	dp[0][0][1] = v[0][0];

	rep(i, r) {
		rep(j, c) {
			const lint val = v[i][j];

			if (val != 0) {
				if (i != 0) {
					for (int k = 0; k <= 3; ++k) {
						chmax(dp[i][j][1], dp[i - 1][j][k] + val);
					}
				}
				if (j != 0) {
					for (int k = 0; k <= 2; ++k) {
						chmax(dp[i][j][k + 1], dp[i][j - 1][k] + val);
					}
				}
			}
			for (int k = 0; k <= 3; ++k) {
				if (i != 0) chmax(dp[i][j][0], dp[i - 1][j][k]);
				if (j != 0) chmax(dp[i][j][k], dp[i][j - 1][k]);
			}
		}
	}

	lint ans = 0;

	for (int i = 0; i <= 3; ++i) {
		ans = max(ans, dp[r - 1][c - 1][i]);
	}

	cout << ans << endl;
}

Measured memory_bytes: 358596