#include "fish.h"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
ll pref[3005][3005], dp[3005][3005][2], pmx1[3005][3005];
ll max_weights(int N, int M, vector<int> X, vector<int> Y, vector<int> W) {
for(int i=0; i<M; i++) pref[X[i]+1][Y[i]+1] += W[i];
for(int i=1; i<=N; i++)
for(int j=1; j<=N; j++) pref[i][j] += pref[i][j-1];
for(int i=1; i<=N; i++)
for(int j=0; j<=N; j++) pmx1[i][j] = -1e18;
pmx1[1][0] = dp[1][0][1] - pref[1][0];
for(int i=1; i<=N; i++) pmx1[1][i] = max(pmx1[1][i-1], dp[1][i][1] - pref[1][i]);
for(int i=2; i<=N; i++) {
for(int j=0; j<=N; j++) {
dp[i][j][1] = max(dp[i][j][1], pmx1[i-1][j] + pref[i-1][j]);
for(int k=0; k<=N; k++) {
if(j <= k) dp[i][j][0] = max(dp[i][j][0], (max(dp[i-1][k][0], dp[i-1][k][1]) + pref[i][k]) - pref[i][j]);
if(i >= 3) dp[i][j][0] = max(dp[i][j][0], max(dp[i-2][k][0], dp[i-2][k][1]) + max(pref[i-1][j], pref[i-1][k]));
if(i >= 3) dp[i][j][1] = max(dp[i][j][1], max(dp[i-2][k][0], dp[i-2][k][1]) + max(pref[i-1][j], pref[i-1][k]));
}
if(j) pmx1[i][j] = pmx1[i][j-1];
pmx1[i][j] = max(pmx1[i][j], dp[i][j][1] - pref[i][j]);
}
}
ll ans = 0;
for(int i=1; i<=N; i++)
for(int j=1; j<=N; j++) ans = max({ ans, dp[i][j][0] + pref[i+1][j], dp[i][j][1] + pref[i+1][j] });
return ans;
}
