#include <unordered_map>
#include <unordered_set>
#include <algorithm>
#include <iostream>
#include <iostream>
#include <fstream>
#include <numeric>
#include <cstring>
#include <cassert>
#include <string>
#include <vector>
#include <queue>
#include <deque>
#include <cmath>
#include <set>
#include <map>
#include <functional>
#include <bitset>
#include <iomanip>
#include <stack>
#include <list>
using namespace std;
#define     loop(n,i,a)     for(ll i=a;i<n;i++)
#define     loopR(n,i,a)    for(ll i=n-1;i>=a;i--)
#define     all(arr,n)      arr,arr+n
#define     allv(v)         (v).begin(),(v).end()
#define     rallv(v)        (v).rbegin(),(v).rend()
#define     m_p             make_pair
#define     ll              long long
#define     pii             pair<ll,ll>
#define     vi              vector<int>
#define     vll             vector<ll>
#define     vii             vector<pair<ll,ll>>
#define     sz(x)           (int)x.size()
#define     pb              push_back
#define     endl            "\n"
#define     Endl            "\n"
#define     f               first
#define     s               second
#define     mem(dp,n)       memset(dp,n,sizeof dp)
int dx[] = { 1 , 0 ,-1 , 0 ,-1 ,-1 , 1 , 1 };
int dy[] = { 0 , 1 , 0 ,-1 ,-1 , 1 ,-1 , 1 };
int KnightI[] = { 2, 1, -1, -2, -2, -1, 1, 2 };
int KnightJ[] = { 1, 2, 2, 1, -1, -2, -2, -1 };
template<typename T>
void max_self(T &a,T b){
    a=max(a,b);
}
template<typename T>
void min_self(T &a,T b){
    a=min(a,b);
}
void fast(){
    std::ios_base::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(NULL);
}
vector<string> vec_splitter(string s) {
    s += ',';
    vector<string> res;
    while(!s.empty()) {
        res.push_back(s.substr(0, s.find(',')));
        s = s.substr(s.find(',') + 1);
    }
    return res;
}
void debug_out(
        vector<string> __attribute__ ((unused)) args,
        __attribute__ ((unused)) int idx,
        __attribute__ ((unused)) int LINE_NUM) { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(vector<string> args, int idx, int LINE_NUM, Head H, Tail... T) {
    if(idx > 0) cerr << ", "; else cerr << "Line(" << LINE_NUM << ") ";
    stringstream ss; ss << H;
    cerr << args[idx] << " = " << ss.str();
    debug_out(args, idx + 1, LINE_NUM, T...);
}
#define debug(...) debug_out(vec_splitter(#__VA_ARGS__), 0, __LINE__, __VA_ARGS__)
const ll mxN=2e4+10,oo=0x3f3f3f3f,MOD=998244353;
const double PI = acos(-1);
int r,c,k;
ll grid[3005][3005],dp[3005][3005][5];
bool valid(int i,int j){
    return i>=1&&i<=r&&j>=1&&j<=c;
}
ll go(int i,int j,int st){
    //cout<<i<<' '<<j<<' '<<st<<endl;
    if(i==r&&j==c)
        return 0;
    ll &ret=dp[i][j][st];
    if(~ret)
        return ret;
    loop(2,z,0){
        int ti=dx[z]+i,tj=dy[z]+j;
        if(valid(ti,tj)){
            if(ti==i){
                if(st==3)
                    ret=max(ret,go(ti,tj,st));
                else
                    ret=max({ret,go(ti,tj,st+1)+grid[ti][tj],go(ti,tj,st)});
            }
            else{
                ret=max({ret,go(ti,tj,1)+grid[ti][tj],go(ti,tj,0)});
            }
        }
    }
    return ret;
}
void solve(){
    cin>>r>>c>>k;
    loop(k,i,0){
        int ri,ci,v;
        cin>>ri>>ci>>v;
        grid[ri][ci]=v;
    }
    mem(dp,-1);
    cout<<max(go(1,1,0),go(1,1,1)+grid[1][1])<<endl;
}
int main() {
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    fast();
    solve();
}

Measured memory_bytes: 427508