#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#include "fish.h"
ll dp[3001][3001][3];
int grid[3001][3001];
int N;
long long f(int x, int y, int flag){
if (dp[x][y][flag]!=-1) return dp[x][y][flag];
if (flag==1){
dp[x][y][flag]=0;
if (y<N){
ll crr = 0;
if (x>0) crr = grid[x-1][y];
dp[x][y][flag]=crr+f(x,y+1,1);
}
if (x+1<N){
dp[x][y][flag]=max(dp[x][y][flag],f(x+1,y,1));
dp[x][y][flag]=max(dp[x][y][flag],f(x+1,y,0));
}
}
else if (flag==0){
dp[x][y][flag]=0;
if (y-1>=0){
dp[x][y][flag]=grid[x][y-1]+f(x,y-1,0);
}
if (x+1<N){
dp[x][y][flag]=max(dp[x][y][flag],f(x+1,y,0));
if (y==0){
dp[x][y][flag]=max(dp[x][y][flag],f(x+1,y,2));
}
}
}
else {
dp[x][y][flag]=0;
if (y<N){
dp[x][y][flag]=f(x,y+1,2);
}
if (x+1<N){
dp[x][y][flag]=max(dp[x][y][flag],f(x+1,y,1));
dp[x][y][flag]=max(dp[x][y][flag],f(x+1,y,0));
}
}
if (flag!=0 && x+2<N){
dp[x][y][flag]=max(dp[x][y][flag],f(x+2,0,1));
}
return dp[x][y][flag];
};
long long max_weights(int _N, int M, std::vector<int> X, std::vector<int> Y, std::vector<int> W) {
N=_N;
for (int i = 0; i < N+1; i++){
for (int j = 0; j < N+1; j++){
grid[i][j]=0;
dp[i][j][0]=dp[i][j][1]=dp[i][j][2]=-1;
}
}
for (int i = 0; i < M; ++i)
{
grid[X[i]][Y[i]]=W[i];
}
//0 decreasing
//1 increasing
//2 increasing, \
but forbidden to profit from back
return f(0,0,2);
}
