#include <bits/stdc++.h>
using namespace std;

template<typename T, typename U>
using pv=vector<pair<T,U>>;
template<typename T>
using matrix=vector<vector<T>>;
template<typename T>
using pque=priority_queue<T>;
template<typename T>
using lpque=priority_queue<T,vector<T>,greater<T>>;

using ll=long long;
using intpair=pair<int,int>;
using llpair=pair<ll,ll>;
using ilpair=pair<int,ll>;
using lipair=pair<ll,int>;
using intvec=vector<int>;
using llvec=vector<ll>;
using intq=queue<int>;
using llq=queue<ll>;
using intmat=vector<intvec>;
using llmat=vector<llvec>;

#define PI 3.141592653589793
#define INTINF ((1<<30)-1)
#define LLINF ((1LL<<62)-1)
#define MPRIME 1000000007
#define MPRIME9 998244353
#define MMPRIME ((1ll<<61)-1)

#define len length()
#define pushb push_back
#define fi first
#define se second

#define setpr fixed<<setprecision(15)
#define all(name) name.begin(),name.end()
#define rall(name) name.rbegin(),name.rend()
#define gsort(vbeg,vend) sort(vbeg,vend,greater<>())

template<class T>
inline bool chmin(T& a, T b) {
	if (a > b) {
		a = b;
		return true;
	}
	return false;
}

template<class T>
inline bool chmax(T& a, T b) {
	if (a < b) {
		a = b;
		return true;
	}
	return false;
}

template<class T>
inline void init(T& v) {
	for(auto &a: v) cin>>a;
}
template<class T, class U>
inline void init(vector<pair<T,U>>& v) {
	for(auto &a: v) cin>>a.first>>a.second;
}
template<class T, class N>
inline void init(T& v, N n) {
	v.resize(n);
	for(auto &a: v) cin>>a;
}
template<class T, class U, class N>
inline void init(vector<pair<T,U>>& v, N n) {
	v.resize(n);
	for(auto &a: v) cin>>a.first>>a.second;
}

inline void out() {
	cout<<endl;
}
template<class T, class... U>
inline void out(T a, U... alist) {
	cout<<a<<" ";
	out(forward<U>(alist)...);
}

template<class N>
void resiz(N n) {
	//empty
}
template<class N, class T, class... U>
void resiz(N n, T&& hd, U&&... tl) {
	hd.resize(n);
	resiz(n,forward<U>(tl)...);
}

bool isout(int h, int w, int H, int W) {
	return ( h<0 || h>=H || w<0 || w>=W );
}

ll binpow(ll a, ll ex, ll p) {
	ll result=1;
	while(ex>0) {
		if(ex&1) result=result*a%p;
		ex>>=1;
		a=a*a%p;
	}
	return result;
}


template<class T>
class Matrix{
	vector<vector<T>> mat;

public:

	Matrix(int h, int w, T n=0) { make(h,w,n); }

	void make(int h, int w) {
		mat=vector<vector<T>>(h,vector<T>(w));
	}
	void make(int h, int w, T init) {
		mat=vector<vector<T>>(h,vector<T>(w,init));
	};

	void in() {
		for(int i=0; i<mat.size(); i++) for(int j=0; j<mat[i].size(); j++) {
			cin>>mat[i][j];
		}
	}

	void out() {
		for(int i=0; i<mat.size(); i++) {
			int wm=mat[i].size();
			for(int j=0; j<wm; j++) {
				cout<<mat[i][j]<<(wm==j+1 ? '\n' : ' ');
			}
		}
		cout<<flush;
	}

	inline vector<T> &operator[](int idx) {
		assert(0<=idx && idx<mat.size());
		return mat[idx];
	}
};


int R,C,K;
Matrix<ll> maps(3000,3000,0);
ll dp[3001][3001][4];

void input() {
	cin>>R>>C>>K;
	for(int i=0; i<K; i++) {
		int r,c; ll v; cin>>r>>c>>v;
		r--, c--;
		maps[r][c]=v;
	}
}

void solve() {
	if(maps[0][0]) {
		dp[0][0][1]=maps[0][0];
	}
	for(int i=0; i<R; i++) for(int j=0; j<C; j++) for(int k=0; k<4; k++) {
		if(k==3) {
			if(i+1<R) {
				chmax(dp[i+1][j][0],dp[i][j][3]);
				chmax(dp[i+1][j][1],dp[i][j][3]+maps[i+1][j]);
			}
			if(j+1<C) chmax(dp[i][j+1][3],dp[i][j][3]);
		}
		else {
			if(i+1<R) {
				chmax(dp[i+1][j][0],dp[i][j][k]);
				chmax(dp[i+1][j][1],dp[i][j][k]+maps[i+1][j]);
			}
			if(j+1<C) {
				chmax(dp[i][j+1][k+1],dp[i][j][k]+maps[i][j+1]);
				chmax(dp[i][j+1][k],dp[i][j][k]);
			}
		}
	}

	ll ans=0;
	for(int i=0; i<4; i++) {
		chmax(ans,dp[R-1][C-1][i]);
	}
	cout<<ans<<endl;
}

int main() {
	cin.tie(nullptr);
	ios_base::sync_with_stdio(false);
	cout<<fixed<<setprecision(15);
	int t=1;
	while(t) {
		input();
		solve();
		t--;
	}
}


Measured memory_bytes: 355376