#include <bits/stdc++.h>
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
using namespace std;
/*----------------------------------ここからマクロ----------------------------------*/
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()
#define vecin(a) rep(i,a.size())cin >> a[i]
#define vecout(a) rep(i,a.size()){cout << a[i];cout << (i == a.size() - 1 ? "\n":" ");}
#define overload4(_1,_2,_3,_4,name,...) name
#define rep1(n) for(int i=0;i<n;++i)
#define rep2(i,n) for(int i=0;i<n;++i)
#define rep3(i,a,b) for(int i=a;i<b;++i)
#define rep4(i,a,b,c) for(int i=a;i<b;i+=c)
#define rep(...) overload4(__VA_ARGS__,rep4,rep3,rep2,rep1)(__VA_ARGS__)
#define rrep1(n) for(int i=n-1;i>=0;i--)
#define rrep2(i,n) for(int i=n-1;i>=0;i--)
#define rrep3(i,a,b) for(int i=a-1;i>=b;i--)
#define rrep4(i,a,b,c) for(int i=a-1;i>=b;i-=c)
#define rrep(...) overload4(__VA_ARGS__,rrep4,rrep3,rrep2,rrep1)(__VA_ARGS__)
#define mp make_pair
#define debug(x) cerr << #x << ": " << x << "\n"
#define doset(x) cout << fixed << setprecision(x)
struct myset{myset(){ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);}};
using ll = long long;
using ld = long double;
using namespace std;
using dou = double;
const int inf = 1 << 30;
const ll INF = 1LL << 60;
const dou pi = 3.14159265358;
const ll mod1 = 1000000007LL;
const ll mod2 = 998244353LL;
typedef pair<ll,ll> P;
ostream &operator<<(ostream &os, const P q){os << q.first << "," << q.second;return os;}
template<class T, class U> inline bool chmin(T& a, const U& b){ if(a > b){ a = b; return 1; } return 0; }
template<class T, class U> inline bool chmax(T& a, const U& b){ if(a < b){ a = b; return 1; } return 0; }
template<class T, class U> inline bool change(T& a,U& b){if(a > b){swap(a,b);return 1;}return 0;}

//nのm乗をMODで割ったあまりO(logm)
ll modpow(ll n,ll m,ll MOD){
    if(m == 0)return 1;
    if(m < 0)return -1;
    ll res = 1;
    while(m){
        if(m & 1)res = (res * n) % MOD;
        m >>= 1;
        n *= n;
        n %= MOD;
    }
    return res;
}

ll mypow(ll n,ll m){
    if(m == 0)return 1;
    if(m < 0)return -1;
    ll res = 1;
    while(m){
        if(m & 1)res = (res * n);
        m >>= 1;
        n *= n;
    }
    return res;
}

//0の場合のアレンジに注意
template<class T>
T gcd(T a,T b){
    a = abs(a);b = abs(b);
    if(a == 0)return b;
    else if(b == 0)return a;
    if(a < b)swap(a,b);
    if(a % b == 0)return b;
    else return gcd(b,a%b);
}
template<class T>
T lcm(T a,T b){
    return a / gcd(a,b) * b;
}

//素数判定O(sqrt(N))
template<class T>
inline bool isp(T n){
    bool res = true;
    if(n == 1)return false;
    else{
        for(ll i = 2;i * i <= n;i++){
            if(n % i == 0){
                res = false;
                break;
            }
        }
        return res;
    }
}

const ll cmax = 1000000;
vector<ll> fac(cmax),finv(cmax),inv(cmax);

// テーブルを作る前処理
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (ll i = 2; i < cmax; i++){
        fac[i] = fac[i - 1] * i % mod1;
        inv[i] = mod1 - inv[mod1%i] * (mod1 / i) % mod1;
        finv[i] = finv[i - 1] * inv[i] % mod1;
    }
}

// 二項係数計算
ll nCk(ll n, ll k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % mod1) % mod1;
}

template<class T = int>
T in(){T x;cin >> x;return x;}

inline bool Yes(bool b){cout << (b ? "Yes\n":"No\n");return b;}
inline bool YES(bool b){cout << (b ? "YES\n":"NO\n");return b;}

/*----------------------------------マクロここまで----------------------------------*/



#define int long long
signed main(){
    myset m;
    int N,M,K;
    cin >> N >> M >> K;
    vector<vector<int>> field(N,vector<int>(M));
    vector<vector<vector<int>>> memo(N,vector<vector<int>>(M,vector<int>(4)));
    int x,y,v;
    rep(i,K){
        cin >> x >> y >> v;
        x--;y--;
        field[x][y] = v;
    }
    const int dx[] = {-1,0};
    const int dy[] = {0,-1};
    memo[0][0][1] = field[0][0];
    rep(i,N){
        rep(j,M){
            rep(k,2){
                int hx = i + dx[k],hy = j + dy[k];
                if(hx < 0 || hy < 0 || hx >= N || hy >= M)continue;
                if(k){
                    if(field[i][j]){
                        rep(l,4)chmax(memo[i][j][l],memo[hx][hy][l]);
                        rep(l,3)chmax(memo[i][j][l + 1],memo[hx][hy][l] + field[i][j]);
                    }
                    else{
                        rep(l,4)chmax(memo[i][j][l],memo[hx][hy][l]);
                    }
                }
                else{
                    if(field[i][j]){
                        rep(l,4)chmax(memo[i][j][1],memo[hx][hy][l] + field[i][j]);
                        rep(l,4)chmax(memo[i][j][0],memo[hx][hy][l]);
                    }
                    else{
                        rep(l,4)chmax(memo[i][j][0],memo[hx][hy][l]);
                    }
                }
            }
        }
    }
    int ans = 0;
    rep(i,4)chmax(ans,memo[N - 1][M - 1][i]);
    cout << ans << "\n";
    /*rep(i,N){
        rep(j,M)cout << field[i][j] << " ";
        cout << "\n";
    }
    cout << "\n";
    rep(i,4){
        rep(j,N){
            rep(k,M){
                cout << memo[j][k][i] << " ";
            }
            cout << "\n";
        }
        cout << "\n";
    }*/
}


Measured memory_bytes: 730216