#include <bits/stdc++.h>
#include <vector>
#include <set>
#include <map>
#include <string>
#include <cstdio>
#include <cstdlib>
#include <climits>
#include <utility>
#include <algorithm>
#include <cmath>
#include <queue>
#include <stack>
#include <iomanip>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp> 
//setbase - cout << setbase (16); cout << 100 << endl; Prints 64
//setfill -   cout << setfill ('x') << setw (5); cout << 77 << endl; prints xxx77
//setprecision - cout << setprecision (14) << f << endl; Prints x.xxxx
//cout.precision(x)  cout<<fixed<<val;  // prints x digits after decimal in val
 
using namespace std;
using namespace __gnu_pbds;
 	// find_by_order()  // order_of_key
typedef tree<
int,
null_type,
less<int>,
rb_tree_tag,
tree_order_statistics_node_update>
ordered_set;
#define f(i,a,b) for(ll i=a;i<b;i++)
#define fi(i,a,b) for(int i=a;i<b;i++)
#define rep(i,n) f(i,0,n)
#define fd(i,a,b) for(ll i=a;i>=b;i--)
#define pb push_back
#define mp make_pair
#define vi vector< int >
#define vl vector< ll >
#define ss second
#define ff first
#define ll long long
#define pii pair< int,int >
#define pll pair< ll,ll >
#define sz(a) a.size()
#define inff (1000*1000*1000+5)
#define all(a) a.begin(),a.end()
#define tri pair<int,pii>
#define vii vector<pii>
#define vll vector<pll>
#define viii vector<tri>
#define pqueue priority_queue< int >
#define pdqueue priority_queue< int,vi ,greater< int > >
#define flush fflush(stdout) 
#define primeDEN 727999983
#define SPEED ios_base::sync_with_stdio(false) ;cin.tie(NULL) ;cout.tie(NULL) ;
#define fp(i,a,n) for(ll i=n-1; i>a ;i--)
#define deb(x) cout << #x << " ---> " << x << endl;
#define X first
#define Y second
#define pia 3.1415926536
#define mod 1000000007
#define mod2 998244353

#define ml map<ll,ll>
#define mll map<pll,ll>
#define vvl vector<vl>
#define vvi vector<vi>
#define letsh(a,b) a<<b
#define rigsh(a,b) a>>b 
mt19937 rng32(chrono::steady_clock::now().time_since_epoch().count()) ;
		bool sortbysec(const pair<int,int> &a, 
		      const pair<int,int> &b) 
		{ 
		    return (a.second < b.second); 
		} 	   
		
		  ll power(ll a,ll n)
		{
		ll ans=1;
		while(n)
		{
		if(n&1) ans=(ans*a)%mod;
		a=(a*a)%mod ;
		n=n>>1;
		 }
		 return ans;
		}
		ll power2(ll a,ll n)
		{
		ll ans =1 ;
		while(n)
		{
			if(n&1) ans =(ans*a) ;
			a = (a*a) ;
			n =n>>1 ;
		  }
		  return ans ;
		}
		ll lcm(ll a, ll b)
		{
		       return a / __gcd(a, b) * b;
		}
#define N 1000030
        ll r,c,k ;ll dp[3003][3003][4] ;vvl a(3003,vl(3003,0)) ;
        ll go(ll i ,ll j ,ll l)
        {
        	
        	if(dp[i][j][l] != -1) return dp[i][j][l] ;
        	ll ans =0 ,mx =0;
        	if(i+1 <=r && l !=0) mx = go(i+1,j,3) +a[i][j] ;
        	else if(i+1 <=r) mx =go(i+1,j,3) ;
        	if(j+1 <=c && l !=0) ans = max(go(i,j+1,l) ,go(i,j+1,l-1) +a[i][j]) ;
		    else if(j+1 <=c) ans = go(i,j+1,l);
		    ans = max(ans,mx) ;
		    //cout<<i<<" "<<j<<" "<<l<<" "<<ans<<" "<<dp[1][2][3]<<endl ;
		    return dp[i][j][l] =ans ;
		}
		               
        void solve()
	    {
	         cin>>r>>c>>k ;
	         f(i,0,r+1) f(j,0,c+1) f(l,0,4) dp[i][j][l] =-1 ;
	         f(i,0,k)
	         {
	         	ll x,y ;cin>>x>>y ;
	         	cin>>a[x][y] ;
			 }
			 f(i,1,4) dp[r][c][i] =a[r][c] ;
	       cout<<go(1,1,3) ;
		  
			 
		} 
			  int main() 
	  	{
	     SPEED
	     ll t =1 ;
	     while(t--) solve() ;
	    }

Measured memory_bytes: 356196