#include "fish.h"
#include <bits/stdc++.h>
#include <vector>
using namespace std;
const int N = 3003;
int n;
long long dp[N][N][2][2];
vector<vector<int>> a;
long long bt(int col, int last, bool me, bool recent) {
if (col > n) {
return 0;
}
if (last > n || last < 0) {
return -1e14;
}
long long& ret = dp[col][last][me][recent];
if (ret != -1) {
return ret;
}
if (me) {
//if (col != 4 || me != true || last != ) {
ret = max(bt(col, last - 1, me, recent) + a[col][last],
bt(col + 1, last, me ^ (last == 0), (last == 0)));
//} else {
//ret = bt(col + 1, last, me ^ (last == 0), (last == 0));
//}
} else {
ret = max(bt(col, last + 1, me, recent) + a[col - 1][last] * (recent == false),
bt(col + 1, last, me ^ (last == n), false));
}
//cout << col << ' ' << last << ' ' << me << ' ' << recent << ' ' << ret << '\n';
return ret;
}
long long max_weights(int N_, int M, vector<int> X, vector<int> Y, vector<int> W) {
n = N_;
a.resize(n + 1);
for (int i = 0; i <= n; ++i) {
a[i].resize(n + 1);
}
for (int i = 0; i < M; ++i) {
a[X[i] + 1][Y[i] + 1] = W[i];
}
memset(dp, -1, sizeof dp);
return bt(1, 0, 0, 0);
}
