Problem:
Score : 500 points

Problem Statement

There are K items placed on a grid of squares with R rows and C columns. Let (i, j) denote the square at the i-th row (1 \leq i \leq R) and the j-th column (1 \leq j \leq C). The i-th item is at (r_i, c_i) and has the value v_i.

Takahashi will begin at (1, 1), the start, and get to (R, C), the goal. When he is at (i, j), he can move to (i + 1, j) or (i, j + 1) (but cannot move to a non-existent square).

He can pick up items on the squares he visits, including the start and the goal, but at most three for each row. It is allowed to ignore the item on a square he visits.

Find the maximum possible sum of the values of items he picks up.

Constraints

1 \leq R, C \leq 3000

1 \leq K \leq \min(2 \times 10^5, R \times C)

1 \leq r_i \leq R

1 \leq c_i \leq C

(r_i, c_i) \neq (r_j, c_j) (i \neq j)

1 \leq v_i \leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

R C K
r_1 c_1 v_1
r_2 c_2 v_2
:
r_K c_K v_K

Output

Print the maximum possible sum of the values of items Takahashi picks up.

Sample Input 1

2 2 3
1 1 3
2 1 4
1 2 5

Sample Output 1

8

He has two ways to get to the goal:

Visit (1, 1), (1, 2), and (2, 2), in this order. In this case, the total value of the items he can pick up is 3 + 5 = 8.

Visit (1, 1), (2, 1), and (2, 2), in this order. In this case, the total value of the items he can pick up is 3 + 4 = 7.

Thus, the maximum possible sum of the values of items he picks up is 8.

Sample Input 2

2 5 5
1 1 3
2 4 20
1 2 1
1 3 4
1 4 2

Sample Output 2

29

We have four items in the 1-st row. The optimal choices are as follows:

Visit (1, 1) (1, 2), (1, 3), (1, 4), (2, 4), and (2, 5), in this order, and pick up all items except the one on (1, 2). Then, the total value of the items he picks up will be 3 + 4 + 2 + 20 = 29.

Sample Input 3

4 5 10
2 5 12
1 5 12
2 3 15
1 2 20
1 1 28
2 4 26
3 2 27
4 5 21
3 5 10
1 3 10

Sample Output 3

142

Solution in Java (OpenJDK 1.8.0) (judge verdict: Runtime Error)

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.InputMismatchException;
import java.util.ArrayList;
import java.io.OutputStreamWriter;
import java.util.LinkedList;
import java.util.NoSuchElementException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Iterator;
import java.io.BufferedWriter;
import java.util.Collection;
import java.io.IOException;
import java.util.List;
import java.io.Writer;
import java.util.Queue;
import java.util.Collections;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);
        EPickingGoods solver = new EPickingGoods();
        solver.solve(1, in, out);
        out.close();
    }

    static class EPickingGoods {
        public void solve(int testNumber, InputReader in, OutputWriter out) {

            int r = in.readInt(), c = in.readInt(), k = in.readInt();


            Indexer<Integer> xs = new Indexer<>();
            Indexer<Integer> ys = new Indexer<>();

            List<Integer> lx = new ArrayList<>();
            List<Integer> ly = new ArrayList<>();

            List<int[]> points = new ArrayList<>();

            for (int i = 0; i < k; ++i) {
                int x = in.readInt() - 1;
                int y = in.readInt() - 1;
                int v = in.readInt();
                lx.add(x);
                ly.add(y);
                points.add(new int[]{x, y, v});
            }

            Collections.sort(lx);
            Collections.sort(ly);

            for (int e : lx) xs.get(e);
            for (int e : ly) ys.get(e);


            int[][] grid = new int[xs.size() + 1][ys.size() + 1];

            for (int[] p : points) {
                int x = p[0];
                int y = p[1];
                int v = p[2];
                grid[xs.get(x)][ys.get(y)] = v;
            }

            long[][][] state = new long[xs.size() + 1][ys.size() + 1][4];


            Queue<EPickingGoods.State> queue = new LinkedList<>();


            queue.add(new EPickingGoods.State(0, 0, 0, 0));
            state[0][0][0] = 0;

            if (grid[0][0] > 0) {
                state[0][0][1] = grid[0][0];
                queue.add(new EPickingGoods.State(0, 0, 1, grid[0][0]));
            }

            while (!queue.isEmpty()) {
                EPickingGoods.State cur = queue.poll();
                int x = cur.x;
                int y = cur.y;
                long cost = cur.cost;
                int moves = cur.moves;
                if (x + 1 == r && y + 1 == c)
                    break;

                if (x + 1 < r && cur.cost > state[cur.x + 1][y][0]) {
                    queue.add(new EPickingGoods.State(x + 1, y, 0, cost));
                    state[x + 1][y][0] = cost;
                }
                if (y + 1 < c && cost > state[x][y + 1][moves]) {
                    queue.add(new EPickingGoods.State(x, y + 1, moves, cost));
                    state[x][y + 1][moves] = cost;
                }

                if (x + 1 < r && cost + grid[x + 1][y] > state[x + 1][y][1]) {
                    queue.add(new EPickingGoods.State(x + 1, y, 1, cost + grid[x + 1][y]));
                    state[x + 1][y][1] = cost + grid[x + 1][y];
                }
                if (moves < 3 && y + 1 < c && cost + grid[x][y + 1] > state[x][y + 1][moves + 1]) {
                    state[x][y + 1][moves + 1] = cost + grid[x][y + 1];
                    queue.add(new EPickingGoods.State(x, y + 1, moves + 1, cost + grid[x][y + 1]));
                }
            }

            out.printLine(ArrayUtils.maxElement(state[r - 1][c - 1]));

        }

        static class State {
            int x;
            int y;
            int moves;
            long cost;

            public State(int x, int y, int m, long c) {
                this.x = x;
                this.y = y;
                this.moves = m;
                this.cost = c;
            }

        }

    }

    static class ArrayUtils {
        public static long maxElement(long[] array) {
            return new LongArray(array).max();
        }

    }

    static class LongArray extends LongAbstractStream implements LongList {
        private long[] data;

        public LongArray(long[] arr) {
            data = arr;
        }

        public int size() {
            return data.length;
        }

        public long get(int at) {
            return data[at];
        }

        public void removeAt(int index) {
            throw new UnsupportedOperationException();
        }

    }

    static interface LongStream extends Iterable<Long>, Comparable<LongStream> {
        public LongIterator longIterator();

        default public Iterator<Long> iterator() {
            return new Iterator<Long>() {
                private LongIterator it = longIterator();

                public boolean hasNext() {
                    return it.isValid();
                }

                public Long next() {
                    long result = it.value();
                    it.advance();
                    return result;
                }
            };
        }

        default public int compareTo(LongStream c) {
            LongIterator it = longIterator();
            LongIterator jt = c.longIterator();
            while (it.isValid() && jt.isValid()) {
                long i = it.value();
                long j = jt.value();
                if (i < j) {
                    return -1;
                } else if (i > j) {
                    return 1;
                }
                it.advance();
                jt.advance();
            }
            if (it.isValid()) {
                return 1;
            }
            if (jt.isValid()) {
                return -1;
            }
            return 0;
        }

        default public long max() {
            long result = Long.MIN_VALUE;
            for (LongIterator it = longIterator(); it.isValid(); it.advance()) {
                long current = it.value();
                if (current > result) {
                    result = current;
                }
            }
            return result;
        }

    }

    static interface LongList extends LongReversableCollection {
        public abstract long get(int index);

        public abstract void removeAt(int index);

        default public LongIterator longIterator() {
            return new LongIterator() {
                private int at;
                private boolean removed;

                public long value() {
                    if (removed) {
                        throw new IllegalStateException();
                    }
                    return get(at);
                }

                public boolean advance() {
                    at++;
                    removed = false;
                    return isValid();
                }

                public boolean isValid() {
                    return !removed && at < size();
                }

                public void remove() {
                    removeAt(at);
                    at--;
                    removed = true;
                }
            };
        }

    }

    static class InputReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private InputReader.SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public int readInt() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            int res = 0;
            do {
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            } while (!isSpaceChar(c));
            return res * sgn;
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);

        }

    }

    static interface LongReversableCollection extends LongCollection {
    }

    static interface LongIterator {
        public long value() throws NoSuchElementException;

        public boolean advance();

        public boolean isValid();

    }

    static class Indexer<K> extends HashMap<K, Integer> {
        private int index = 0;

        public Integer get(Object key) {
            if (!containsKey(key)) {
                put((K) key, index++);
            }
            return super.get(key);
        }

    }

    static interface LongCollection extends LongStream {
        public int size();

    }

    static class OutputWriter {
        private final PrintWriter writer;

        public OutputWriter(OutputStream outputStream) {
            writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
        }

        public OutputWriter(Writer writer) {
            this.writer = new PrintWriter(writer);
        }

        public void close() {
            writer.close();
        }

        public void printLine(long i) {
            writer.println(i);
        }

    }

    static abstract class LongAbstractStream implements LongStream {
        public String toString() {
            StringBuilder builder = new StringBuilder();
            boolean first = true;
            for (LongIterator it = longIterator(); it.isValid(); it.advance()) {
                if (first) {
                    first = false;
                } else {
                    builder.append(' ');
                }
                builder.append(it.value());
            }
            return builder.toString();
        }

        public boolean equals(Object o) {
            if (!(o instanceof LongStream)) {
                return false;
            }
            LongStream c = (LongStream) o;
            LongIterator it = longIterator();
            LongIterator jt = c.longIterator();
            while (it.isValid() && jt.isValid()) {
                if (it.value() != jt.value()) {
                    return false;
                }
                it.advance();
                jt.advance();
            }
            return !it.isValid() && !jt.isValid();
        }

        public int hashCode() {
            int result = 0;
            for (LongIterator it = longIterator(); it.isValid(); it.advance()) {
                result *= 31;
                result += it.value();
            }
            return result;
        }

    }
}