#include <bits/stdc++.h>
using namespace std;
using ll = long long; using pii = pair<ll,ll>;
const ll INF = 1e18;
ll ans = -1;
map<ll,ll> xh; //x->y
map<ll,ll> xhF; //y->x
map<ll,ll> yh; //y->x
map<ll,ll> yhF; //x->y
pii pqry = {-1,-1};
bool ivp(pii p1, pii p2) {
return (((p1.first<p2.first)&&(p1.second>p2.second))||((p1.first>p2.first)&&(p1.second<p2.second)));
}
ll qry(pii p0) { //qry to change min
if (pqry.first==-1) {
return INF;
}
if (pqry.first>p0.first && pqry.second>p0.second) {
return (pqry.first+pqry.second);
}
return INF;
}
void fX(ll x1, pii padd = {-1,-1}) {
auto A0 = xh.find(x1);
if (A0==xh.end() || A0==xh.begin()) {
return;
}
A0--;
if ((*A0).second>=xh[x1]) {
pii pdel = *A0;
xh.erase(A0);
xhF.erase(xhF.find(pdel.second));
if (padd.first!=-1) {
xhF[padd.second]=padd.first;
}
fX(x1,padd);
}
}
void updX(pii p0) {
ll x1 = p0.first; ll y1 = p0.second;
auto A0 = xh.lower_bound(x1);
if (A0==xh.end() || (*A0).second>y1) {
if (A0!=xh.end() && (*A0).first==x1) {
pii pdel = *A0;
xh.erase(A0);
xhF.erase(xhF.find(pdel.second));
}
xh[x1]=y1;
xhF[y1]=x1;
fX(x1, p0); //fix X
}
}
void fY(ll x1, pii padd = {-1,-1}) {
auto A0 = yh.find(x1);
if (A0==yh.end() || A0==yh.begin()) {
return;
}
A0--;
//cout << "ftest\n";
if ((*A0).second>=yh[x1]) {
//cout << "f1\n";
pii pdel = *A0;
//cout << "wipe (fY) pdel = "<<pdel.first<<","<<pdel.second<<"\n";
yh.erase(A0);
yhF.erase(yhF.find(pdel.second));
if (padd.first!=-1) {
yhF[padd.second]=padd.first;
}
fY(x1, padd);
}
}
void updY(pii p0) {
ll x1 = p0.first; ll y1 = p0.second;
auto A0 = yh.lower_bound(x1);
if (A0==yh.end() || (*A0).second>y1) {
if (A0 != yh.end() && (*A0).first==x1) {
pii pdel = *A0;
//cout << "wipe (updY) pdel = "<<pdel.first<<","<<pdel.second<<"\n";
yh.erase(A0);
yhF.erase(yhF.find(pdel.second));
}
yh[x1]=y1;
yhF[y1]=x1;
fY(x1,p0); //fix X
}
}
void pupd(pii p0, pii pext) {
if (!ivp(p0,pext)) {
return;
}
pii pnew = {max(p0.first,pext.first),max(p0.second,pext.second)};
assert(((pqry.first<=pnew.first)&&(pqry.second<=pnew.second))||((pqry.first>=pnew.first)&&(pqry.second>=pnew.second)));
pqry = {max(pqry.first,pnew.first),max(pqry.second,pnew.second)};
}
set<pii> alrc; //already inserted
void upd(pii p0) { //insert into hull
if (alrc.find(p0)!=alrc.end()) {
return;
}
alrc.insert(p0);
updX(p0);
updY({p0.second,p0.first});
auto A0 = xhF.lower_bound(p0.second);
if (A0!=xhF.begin()) {
A0--;
//cout << "f1\n";
pupd(p0,{(*A0).second,(*A0).first});
}
auto A1 = yhF.lower_bound(p0.first);
if (A1 != yhF.begin()) {
A1--;
//cout << "f2\n";
pupd(p0,{(*A1).first,(*A1).second});
}
}
int main() {
ll N; cin >> N;
map<ll,vector<pii>> mxyz;
for (ll i=0;i<N;i++) {
ll x1,y1,z1; cin >> x1 >> y1 >> z1;
mxyz[x1].push_back({y1,z1});
}
for (auto A0: mxyz) {
ll x1 = A0.first;
vector<pii> vyz = A0.second;
for (pii p0: vyz) {
ll qryV = qry(p0);
if (qryV<INF && qryV>0) {
ans = max(ans,x1+qryV);
}
//ans = max(ans,x1+qry(p0)); //*pretend* that this is now {x,y}
//cout << "x1, qry(p0)="<<x1<<","<<qry(p0)<<"\n";
}
for (pii p0: vyz) {
upd(p0);
// cout << "PRINT NEW CYCLE\n";
// cout << "xh: \n";
// for (pii p0: xh) {
// cout << p0.first << " " <<p0.second<<"\n";
// }
// cout << "yh: \n";
// for (pii p0: yh) {
// cout << p0.first << " " <<p0.second<<"\n";
// }
// cout << "xhF: \n";
// for (pii p0: xhF) {
// cout << p0.first << " " <<p0.second<<"\n";
// }
// cout << "yhF: \n";
// for (pii p0: yhF) {
// cout << p0.first << " " <<p0.second<<"\n";
// }
}
// cout << "PRINT NEW CYCLE\n";
// cout << "xh: \n";
// for (pii p0: xh) {
// cout << p0.first << " " <<p0.second<<"\n";
// }
// cout << "yh: \n";
// for (pii p0: yh) {
// cout << p0.first << " " <<p0.second<<"\n";
// }
// cout << "xhF: \n";
// for (pii p0: xhF) {
// cout << p0.first << " " <<p0.second<<"\n";
// }
// cout << "yhF: \n";
// for (pii p0: yhF) {
// cout << p0.first << " " <<p0.second<<"\n";
// }
}
if (ans == INF) {
cout << "-1\n";
} else {
cout << ans << "\n";
}
}
