// Create your own template by modifying this file!
#include <string>
#include <vector>
#include <climits>
#include <cstring>
#include <map>
#include <queue>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <iostream>
#include <set>
#include <unordered_set>
#include <unordered_map>
#include <cassert>
#include <deque>
#include <stack>
#include <functional>
#define SZ(X) ((int)(X).size())
#define ALL(X) (X).begin(), (X).end()
#define REP(I, N) for (int I = 0; I < (N); ++I)
#define REPP(I, A, B) for (int I = (A); I < (B); ++I)
#define FOR(I, A, B) for (int I = (A); I <= (B); ++I)
#define FORS(I, S) for (int I = 0; S[I]; ++I)
#define RS(X) scanf("%s", (X))
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()), c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
#define GET_POS(c,x) (lower_bound(c.begin(),c.end(),x)-c.begin())
#define CASET int ___T; scanf("%d", &___T); for(int cs=1;cs<=___T;cs++)
#define MP make_pair
#define PB emplace_back
#define MS0(X) memset((X), 0, sizeof((X)))
#define MS1(X) memset((X), -1, sizeof((X)))
#define LEN(X) strlen(X)
#define F first
#define S second
using namespace std;
typedef long long LL;
typedef unsigned long long ULL;
typedef long double LD;
typedef pair<int,int> PII;
typedef vector<int> VI;
typedef vector<LL> VL;
typedef vector<PII> VPII;
typedef pair<LL,LL> PLL;
typedef vector<PLL> VPLL;
template<class T> void _R(T &x) { cin >> x;  }
void _R(int &x) { scanf("%d", &x);  }
void _R(int64_t &x) { scanf("%lld", &x);  }
void _R(double &x) { scanf("%lf", &x);  }
void _R(char &x) { scanf(" %c", &x);  }
void _R(char *x) { scanf("%s", x);  }
void R() {}
template<class T, class... U> void R(T &head, U &... tail) { _R(head); R(tail...);  }
template<class T> void _W(const T &x) { cout << x;  }
void _W(const int &x) { printf("%d", x);  }
void _W(const int64_t &x) { printf("%lld", x);  }
void _W(const double &x) { printf("%.16f", x);  }
void _W(const char &x) { putchar(x);  }
void _W(const char *x) { printf("%s", x);  }
template<class T,class U> void _W(const pair<T,U> &x) {_W(x.F); putchar(' '); _W(x.S);}
template<class T> void _W(const vector<T> &x) { for (auto i = x.begin(); i != x.end(); _W(*i++)) if (i != x.cbegin()) putchar(' ');  }
void W() {}
template<class T, class... U> void W(const T &head, const U &... tail) { _W(head); putchar(sizeof...(tail) ? ' ' : '\n'); W(tail...);  }
#ifdef DEBUG
 #define debug(...) {printf("[DEBUG] ");W(__VA_ARGS__);}
#else
 #define debug(...)
#endif
int MOD = 1e9+7;
void ADD(LL& x,LL v){x=(x+v)%MOD;if(x<0)x+=MOD;}
/*}}}*/
const int SIZE = 1<<20;

int v[3003][3003];
LL dp[2][3003][4];

void solve() {
    int r, c, K;
    R(r, c, K);
    while (K--) {
        int r, c;
        R(r, c);
        r--; c--;
        R(v[r][c]);
    }
    REP(i, r) {
        memset(dp[i%2], 0, sizeof dp[i%2]);
        REP(j, c) {
            REP(k, 4) {
                if (i > 0) {
                    dp[i%2][j][0] = max(dp[i%2][j][0], dp[(i-1)%2][j][k]);
                }
                if (j > 0) {
                    dp[i%2][j][k] = max(dp[i%2][j][k], dp[i%2][j-1][k]);
                }
            }
            for (int k = 3; k; k--) {
                dp[i%2][j][k] = max(dp[i%2][j][k], dp[i%2][j][k-1] + v[i][j]);
            }
            REP(k, 4) {
                debug(i, j, k, dp[i%2][j][k]);
            }
        }
    }
    LL ans = 0;
    REP(k, 4) {
        ans = max(ans, dp[(r-1)%2][c-1][k]);
    }
    W(ans);
}

int main() {
#define MULTITEST 0
#if MULTITEST    
    CASET{
        solve();
    }
#else
    solve();
#endif
    return 0;
}


Measured memory_bytes: 38528