#pragma GCC target("avx2,avx")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std;
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//using namespace __gnu_pbds;
//using i128 = __int128_t;
using ll = long long;
using ull = unsigned long long;
using pii = pair<int, int>;
using pll = pair<long long, long long>;
#define rep(i, n) for(int i = 0; i < (n); ++i)
#define all(x) (x).begin(),(x).end()
#define SZ(x) ((int)(x).size())
constexpr char ln = '\n';
template<class T1, class T2> inline bool chmax(T1 &a, T2 b) {if (a < b) {a = b; return true;} return false;}
template<class T1, class T2> inline bool chmin(T1 &a, T2 b) {if (a > b) {a = b; return true;} return false;}
inline int topbit(int x) {return x == 0 ? -1 : 31-__builtin_clz(x);}
inline int topbit(long long x) {return x == 0 ? -1 : 63-__builtin_clzll(x);}
inline int botbit(int x) {return x == 0 ? 32 : __builtin_ctz(x);}
inline int botbit(long long x) {return x == 0 ? 64 : __builtin_ctzll(x);}
inline int popcount(int x) {return __builtin_popcount(x);}
inline int popcount(long long x) {return __builtin_popcountll(x);}
inline void print() {cout << "\n";}
template<class T>
inline void print(const vector<T> &v) {
    for (auto itr = v.begin(); itr != v.end(); ++itr) cout << *itr << " ";
    print();
}
template<class T, class... Args>
inline void print(const T &x, const Args &... args) {
    cout << x << " ";
    print(args...);
}
#ifdef MINATO_LOCAL
#define dump(x) cerr << __LINE__ << " : " << #x << " = " << (x) << endl;
inline void debug() {cerr << endl;}
template<class T>
inline void debug(const vector<T> &v) {
    for (auto itr = v.begin(); itr != v.end(); ++itr) cerr << *itr << " ";
    debug();
}
template<class T, class... Args>
inline void debug(const T &x, const Args &... args) {
    cerr << x << " ";
    debug(args...);
}
#else
#define dump(x) void(0)
inline void debug() {}
template<class T> inline void debug(const vector<T> &v) {}
template<class T, class... Args> inline void debug(const T &x, const Args &... args) {}
#endif
struct Fast_ios {Fast_ios() {cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20);};} fast_ios;
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

ll dp[3030][3030][4];
int main() {
    int R,C,K;
    cin >> R >> C >> K;
    vector<vector<ll>> A(R, vector<ll>(C,-1e18));
    rep(i,K) {
        int r,c,v; cin >> r >> c >> v;
        --r; --c;
        A[r][c] = v;
    }
 
    if (A[0][0] != -1e18) dp[0][0][1] = A[0][0];
    rep(x,R) {
        rep(y,C) {
            rep(i,4) {
                if (x < R-1) {
                    chmax(dp[x+1][y][0],dp[x][y][i]);
                    if (A[x+1][y] != -1e18) chmax(dp[x+1][y][1],dp[x][y][i]+A[x+1][y]);
                }
                if (y < C-1) {
                    chmax(dp[x][y+1][i],dp[x][y][i]);
                    if (A[x][y+1] != -1e18 and i < 3) {
                        chmax(dp[x][y+1][i+1],dp[x][y][i]+A[x][y+1]);
                    }
                }
            }
        }
    }
 
    ll ans = 0;
    rep(i,R) rep(j,C) rep(k,4) chmax(ans,dp[i][j][k]);
 
    cout << ans << ln;
}

Measured memory_bytes: 357648