#include <bits/stdc++.h>
#define ll long long
#include "fish.h"
using namespace std;
const int N = 3e3 + 5;
const ll oo = -1e16;
int n, m, a[N][N];
ll f[3][N][N], g[3][N][N];
void vin(ll &x,ll y){
x = max(x, y);
}
long long max_weights(int _N, int M, std::vector<int> X, std::vector<int> Y, std::vector<int> W) {
n = _N;
m = M;
for(int i = 1; i <= m; i ++){
int x = X[i - 1] + 1, y = Y[i - 1] + 1, c = W[i - 1];
a[x][y] = c;
}
// for(int i = 1; i <= n; i ++){
// for(int j = 1; j <= n; j ++) cerr << a[i][j] << " ";
// cerr << "\n";
// }
for(int i = 0; i <= n; i ++){
for(int j = 0; j <= n + 1; j ++){
a[i][j] += (j > 0 ? a[i][j - 1] : 0);
for(int k = 0; k <= 1; k ++){
f[k][i][j] = g[k][i][j] = oo;
}
}
}
f[0][0][0] = f[1][0][0] = 0;
g[1][0][0] = 0;
for(int i = 1; i <= n; i ++){
g[1][0][i] = g[1][0][i - 1];
}
// cerr << " g\n";
ll ans = 0;
for(int i = 1; i <= n; i ++){
ll ret = oo;
for(int j = 0; j <= n; j ++) ret = max({ret, f[0][i - 1][j], f[1][i - 1][j]});
f[0][i][0] = f[1][i][0] = ret;
for(int j = 1; j <= n; j ++){
f[1][i][j] = 0;
f[0][i][j] = 0;
vin(f[1][i][j], a[i - 1][j] + g[1][i - 1][j - 1]);
vin(f[0][i][j], g[0][i - 1][j + 1] - a[i][j]);
// cerr << i << " " << j << " " << f[0][i][j] << " " << f[1][i][j] << " h\n";
vin(ans, max(f[1][i][j], f[0][i][j]));
}
for(int j = 0; j <= n; j ++){
g[1][i][j] = f[1][i][j] - a[i][j];
// cerr << 1 << " " << i << " " << j << " " << f[1][i][j] - a[i][j] << " t\n";
if(j > 0) vin(g[1][i][j], g[1][i][j - 1]);
// cerr << " " << 1 << " " << i << " " << j << " " << g[1][i][j] << " uuu\n";
}
for(int j = n; j >= 0; j --){
g[0][i][j] = max(f[0][i][j], f[1][i][j]) + a[i + 1][j];
if(j < n) vin(g[0][i][j], g[0][i][j + 1]);
// cerr << " " << 0 << " " << i << " " << j << " " << g[0][i][j] <<" ooo\n";
}
}
return ans;
}
//#define LOCAL
#ifdef LOCAL
int main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define task "v"
if(fopen(task ".inp","r")){
freopen(task ".inp","r",stdin);
freopen(task ".out","w",stdout);
}
int _N, M;
assert(2 == scanf("%d %d", &_N, &M));
std::vector<int> X(M), Y(M), W(M);
for (int i = 0; i < M; ++i) {
assert(3 == scanf("%d %d %d", &X[i], &Y[i], &W[i]));
}
long long result = max_weights(_N, M, X, Y, W);
printf("%lld\n", result);
return 0;
}
/*
5 4
0 2 5
1 1 2
4 4 1
3 3 3
*'/
#endif // LOCAL
Compilation message
fish.cpp:102:1: error: unterminated comment
102 | /*
| ^
fish.cpp:79: error: unterminated #ifdef
79 | #ifdef LOCAL
|
