#include<bits/stdc++.h>
using namespace std;
#define foru(i,a,b) for(int i=(a); i<=(b); ++i)
#define ford(i,a,b) for(int i=(a); i>=(b); --i)
#define rep(i,a) for(int i=0; i<(a); ++i)
#define sz(a) (int)(a).size()
#define all(a) (a).begin(),(a).end()
#define bit(s,i) (((s)>>(i))&1)
#define ii pair<int,int>
#define fi first
#define se second
#define pb push_back
#define eb emplace_back
#define ll long long
#define _ << " " <<
template <class X, class Y> bool maxi(X &x, Y y){return x<y?x=y,true:false;}
template <class X, class Y> bool mini(X &x, Y y){return x>y?x=y,true:false;}
const int MAX = 3030;
ll dp[MAX][MAX][2],sum[MAX][MAX],weight[MAX][MAX],mxDP[MAX];
ll max_weights(int N, int M, vector<int> X, vector<int> Y, vector<int> W){
assert(N<=3000);
rep(i,M){
++X[i]; ++Y[i];
sum[X[i]][Y[i]]=W[i];
weight[X[i]][Y[i]]=W[i];
}
foru(i,1,N) foru(j,1,N) sum[i][j]+=sum[i][j-1];
foru(j,0,N) dp[0][j][0] = dp[0][j][1] = -1e18;
dp[0][0][0]=0;
foru(i,1,N){
ll mxz = -1e18, mxo = -1e18;
foru(j,0,N){
mxz = max(mxz + weight[i-1][j], dp[i-1][j][0]);
mxo = max(mxo, dp[i-1][j][1]);
dp[i][j][0] = max(mxz, mxo);
}
mxz = -1e18;
ford(j,N,0){
mxz = max(mxz + weight[i][j+1], max(dp[i-1][j][1], dp[i-1][j][0]));
dp[i][j][1] = mxz;
}
if(i>=2){
foru(j,0,N){
dp[i][j][0] = max(dp[i][j][0], mxDP[i-2] + sum[i-1][j]);
dp[i][j][1] = max(dp[i][j][1], mxDP[i-2] + sum[i-1][j]);
}
}
foru(j,0,N){
maxi(mxDP[i], max(dp[i][j][0], dp[i][j][1]));
}
}
return mxDP[N];
}
//int main(){
// cout<<max_weights(5,4,{0,1,4,3},{2,1,4,3},{5,2,1,3});
//}
