#include <bits/stdc++.h>
#define pb push_back
#define fst first
#define snd second
#define fore(i,a,b) for(int i=a,pao=b;i<pao;++i)
#define SZ(x) ((int)x.size())
#define ALL(x) x.begin(),x.end()
#define mset(a,v) memset((a),(v),sizeof(a))
#define FIN ios::sync_with_stdio(0);cin.tie(0);cout.tie(0)
using namespace std;
typedef long long ll;
const int MAXN=3005;
const ll INF=1e18;
ll dp[MAXN][MAXN][2],pref[MAXN][MAXN];
long long max_weights(int N, int M, std::vector<int> X, std::vector<int> Y, std::vector<int> W) {
fore(i,0,M){
pref[X[i]+1][Y[i]+1]+=W[i];
}
fore(i,0,N+1){
fore(j,1,N+1){
pref[i][j]+=pref[i][j-1];
}
}
fore(i,0,N+2)fore(j,0,N+2)fore(k,0,2)dp[i][j][k]=-INF;
ll ans=0;
dp[0][0][1]=0;
fore(i,1,N+1){
vector<ll>prefMax(N+2,-INF),sufMax(N+2,-INF);
fore(x,0,N+1){
prefMax[x]=max((x?prefMax[x-1]:-INF),dp[i-1][x][1]-pref[i-1][x]);
}
for(int x=N;x>=0;x--){
sufMax[x]=max(sufMax[x+1],max(dp[i-1][x][0],dp[i-1][x][1])+pref[i][x]);
}
fore(x,0,N+1){
if(x==0){
dp[i][x][0]=dp[i][x][1]=max(dp[i-1][x][0],dp[i-1][x][1]);
}
dp[i][x][1]=pref[i-1][x]+prefMax[x];
dp[i][x][0]=sufMax[x]-pref[i][x];
ans=max({ans,dp[i][x][1],dp[i][x][0]});
}
}
return ans;
}
