#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define chmax(x,y) x = max(x,y)

int a[3005][3005];
ll dp[3005][3005][4];
 
int main() {
  int R, C, n;
  cin >> R >> C >> n;
  rep(i,n) {
    int r, c, v;
    cin >> r >> c >> v;
    a[r-1][c-1] = v;
  }
 
  rep(i,R)rep(j,C) {
    for (int k = 2; k >= 0; k--) {
      chmax(dp[i][j][k+1], dp[i][j][k]+a[i][j]);
    }
    rep(k,4) {
      chmax(dp[i+1][j][0], dp[i][j][k]);
      chmax(dp[i][j+1][k], dp[i][j][k]);
    }
  }
 
  ll ans = 0;
  rep(k,4) chmax(ans, dp[R-1][C-1][k]);
  cout << ans << endl;
  return 0;
}