#include <bits/stdc++.h>
#define FOR(i, x, y) for (int i = x; i < y; i++)
typedef long long ll;
using namespace std;
struct Node {
ll l, r, tot, best;
Node operator+(Node B) {
return {max(l, tot + B.l), max(B.r, r + B.tot), tot + B.tot, max(max(best, B.best), r + B.l)};
}
} segtree[8001];
struct Obstacle {
ll x, y, v;
bool operator<(Obstacle B) {
if (x == B.x) return y < B.y;
return x < B.x;
}
} obstacles[2001];
int n;
void build(int node = 1, int l = 1, int r = n) {
if (l == r) {
ll v = max(obstacles[l].v, 0ll);
segtree[node] = {v, v, obstacles[l].v, v};
} else {
int mid = (l + r) / 2;
build(node * 2, l, mid);
build(node * 2 + 1, mid + 1, r);
segtree[node] = segtree[node * 2] + segtree[node * 2 + 1];
}
}
void update(int pos, ll val, int node = 1, int l = 1, int r = n) {
if (l == r) segtree[node] = {max(val, 0ll), max(val, 0ll), val, max(val, 0ll)};
else {
int mid = (l + r) / 2;
if (pos > mid) update(pos, val, node * 2 + 1, mid + 1, r);
else update(pos, val, node * 2, l, mid);
segtree[node] = segtree[node * 2] + segtree[node * 2 + 1];
}
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n;
FOR(i, 1, n + 1) cin >> obstacles[i].x >> obstacles[i].y >> obstacles[i].v;
sort(obstacles + 1, obstacles + n + 1);
build();
cout << segtree[1].best;
return 0;
}
