import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.StringJoiner;
import java.util.StringTokenizer;
import java.util.function.IntUnaryOperator;
import java.util.function.LongUnaryOperator;

public class Main {
    static In in = new In();
    static Out out = new Out();
    static final long inf = 0x1fffffffffffffffL;
    static final int iinf = 0x3fffffff;
    static final double eps = 1e-9;
    static long mod = 1000000007;

    void solve() {
        int w = in.nextInt();
        int h = in.nextInt();
        int m = in.nextInt();
        long[][] first = new long[w][h];
        for (int i = 0; i < m; i++) {
            int x = in.nextInt() - 1;
            int y = in.nextInt() - 1;
            first[x][y] = in.nextLong();
        }
        long[][][] dp = new long[w + 1][h + 1][4];
        for (int i = 0; i <= w; i++) {
            for (int j = 0; j <= h; j++) {
                for (int k = 0; k < 4; k++) {
                    dp[i][j][k] = -inf;
                }
            }
        }
        if (first[0][0] > 0) {
            dp[0][0][1] = first[0][0];
        }
        dp[0][0][0] = 0;
        for (int i = 0; i < w; i++) {
            for (int j = 0; j < h; j++) {
                for (int k = 0; k < 4; k++) {
                    dp[i][j + 1][k] = Math.max(dp[i][j + 1][k], dp[i][j][k]);
                    dp[i + 1][j][0] = Math.max(dp[i + 1][j][0], dp[i][j][k]);
                    if (j + 1 < h && first[i][j + 1] > 0 && k <= 2) {
                        dp[i][j + 1][k + 1] = Math.max(dp[i][j + 1][k + 1], dp[i][j][k] + first[i][j + 1]);
                    }
                    if (i + 1 < w && first[i + 1][j] > 0) {
                        dp[i + 1][j][1] = Math.max(dp[i + 1][j][1], dp[i][j][k] + first[i + 1][j]);
                    }
                }
            }
        }
        long ans = -inf;
        for (int i = 0; i < 4; i++) {
            ans = Math.max(ans, dp[w - 1][h - 1][i]);
        }
        out.println(ans);
    }

    public static void main(String[]$) {
        new Main().solve();
        out.flush();
    }
}

class In {
    private BufferedReader reader = new BufferedReader(new InputStreamReader(System.in), 0x10000);
    private StringTokenizer tokenizer;

    String next() {
        try {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                tokenizer = new StringTokenizer(reader.readLine());
            }
        } catch (IOException ignored) {
        }
        return tokenizer.nextToken();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    long nextLong() {
        return Long.parseLong(next());
    }

    char[] nextCharArray() {
        return next().toCharArray();
    }

    char[][] nextCharGrid(int n, int m) {
        char[][] a = new char[n][m];
        for (int i = 0; i < n; i++) {
            a[i] = next().toCharArray();
        }
        return a;
    }

    int[] nextIntArray(int n) {
        int[] a = new int[n];
        for (int i = 0; i < n; i++) {
            a[i] = nextInt();
        }
        return a;
    }

    int[] nextIntArray(int n, IntUnaryOperator op) {
        int[] a = new int[n];
        for (int i = 0; i < n; i++) {
            a[i] = op.applyAsInt(nextInt());
        }
        return a;
    }

    long[] nextLongArray(int n) {
        long[] a = new long[n];
        for (int i = 0; i < n; i++) {
            a[i] = nextLong();
        }
        return a;
    }

    long[] nextLongArray(int n, LongUnaryOperator op) {
        long[] a = new long[n];
        for (int i = 0; i < n; i++) {
            a[i] = op.applyAsLong(nextLong());
        }
        return a;
    }

    List<List<Integer>> nextEdges(int n, int m) {
        List<List<Integer>> res = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            res.add(new ArrayList<>());
        }
        for (int i = 0; i < m; i++) {
            int u = nextInt() - 1;
            int v = nextInt() - 1;
            res.get(u).add(v);
            res.get(v).add(u);
        }
        return res;
    }
}

class Out {
    private PrintWriter out = new PrintWriter(System.out);
    boolean autoFlush = false;

    void println(Object... a) {
        StringJoiner joiner = new StringJoiner(" ");
        for (Object obj : a) {
            joiner.add(String.valueOf(obj));
        }
        out.println(joiner);
        if (autoFlush) {
            out.flush();
        }
    }

    void println(char[] s) {
        out.println(String.valueOf(s));
        if (autoFlush) {
            out.flush();
        }
    }

    void println(int[] a) {
        StringJoiner joiner = new StringJoiner(" ");
        for (int i : a) {
            joiner.add(Integer.toString(i));
        }
        out.println(joiner);
        if (autoFlush) {
            out.flush();
        }
    }

    void println(long[] a) {
        StringJoiner joiner = new StringJoiner(" ");
        for (long i : a) {
            joiner.add(Long.toString(i));
        }
        out.println(joiner);
        if (autoFlush) {
            out.flush();
        }
    }

    void flush() {
        out.flush();
    }
}


Measured memory_bytes: 692020