#include <cstdio>
#include <cassert>
#include <cstring>
#include <algorithm>
#include <vector>
#define X first
#define Y second
#define PB push_back
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
const int N = 4e3 + 10;
int dvade[N][N];
vector<int> x, y, z;
void solve(vector<pair<pii, int>> v) {
memset(dvade, -1, sizeof(dvade));
int n = v.size();
for(auto &i : v) {
x.PB(i.X.X);
y.PB(i.X.Y);
z.PB(i.Y);
}
sort(x.begin(), x.end());
x.erase(unique(x.begin(), x.end()), x.end());
sort(y.begin(), y.end());
y.erase(unique(y.begin(), y.end()), y.end());
sort(z.begin(), z.end());
z.erase(unique(z.begin(), z.end()), z.end());
for(auto &i : v) {
int a = i.X.X, b = i.X.Y, c = i.Y;
int j = lower_bound(x.begin(), x.end(), a) - x.begin() + 1;
int k = lower_bound(y.begin(), y.end(), b) - y.begin() + 1;
// printf("%d %d %d %d %d\n", a, b, c, j, k);
dvade[j][k] = max(dvade[j][k], c);
}
for(int i = 0; i <= n; ++i) {
for(int j = 0; j <= n; ++j) {
if(i) dvade[i][j] = max(dvade[i - 1][j], dvade[i][j]);
if(j) dvade[i][j] = max(dvade[i][j], dvade[i][j - 1]);
// printf("%d ", dvade[i][j]);
}
// printf("\n");
}
int ans = -1;
for(auto &i : v) {
for(auto &j : v) {
int a = i.X.X, b = i.X.Y, c = i.Y;
int a_ = j.X.X, b_ = j.X.Y, c_ = j.Y;
int ind1 = lower_bound(x.begin(), x.end(), a) - x.begin();
int ind2 = lower_bound(y.begin(), y.end(), b_) - y.begin();
assert(ind1 < N && ind2 < N);
if(a > a_ && b < b_ && c < dvade[ind1][ind2] && c_ < dvade[ind1][ind2] && dvade[ind1][ind2] != -1) {
ans = max(ans, a + b_ + dvade[ind1][ind2]);
// printf("%d %d %d | %d %d %d | %d %d %d \n", a, b, c, a_, b_, c_, ind1, ind2, dvade[ind1][ind2]);
}
}
}
printf("%d\n", ans);
}
int main() {
int n;
scanf("%d", &n);
vector<pair<pii, int>> v;
for(; n--; ) {
int x, y, z;
scanf("%d%d%d", &x, &y, &z);
v.PB({{x, y}, z});
}
sort(v.begin(), v.end());
v.erase(unique(v.begin(), v.end()), v.end());
assert((int) v.size() < N);
solve(v);
return 0;
}
