#include<bits/stdc++.h>
#define int long long
#define fi first
#define se second
#define pb push_back
#define ii pair<int, int>
#define sz(v) (int)v.size()
#define all(v) v.begin(), v.end()
using namespace std;
const int N=1.5e5+5, mod = 1e9+7, inf = 1e18;
struct SegTreeMin {
int sz;
vector<int> seg;
SegTreeMin(int n) {
sz = n;
seg.resize(4*n+5, inf);
}
void upd(int node, int l, int r, int idx, int val) {
if(l>idx || r<idx) return;
if(l==r) {
seg[node] = min(seg[node], val);
return;
}
int mid = (l+r)>>1;
upd(node<<1, l, mid, idx, val); upd(node<<1|1, mid+1, r, idx, val);
seg[node] = min(seg[node<<1], seg[node<<1|1]);
}
int get(int node, int l, int r, int ql, int qr) {
if(l>qr || r<ql) return inf;
if(ql<=l && r<=qr) return seg[node];
int mid = (l+r)>>1;
return min(get(node<<1, l, mid, ql, qr), get(node<<1|1, mid+1, r, ql, qr));
}
int walk(int node, int l, int r, int val) {
if(l==r) {
if(seg[node]<val) return l;
return -1;
}
int mid = (l+r)>>1;
if(seg[node<<1|1]<val) {
return walk(node<<1|1, mid+1, r, val);
} else if(seg[node<<1]<val) {
return walk(node<<1, l, mid, val);
} else {
return -1;
}
}
};
struct SegTreeMax {
int sz;
vector<int> seg;
SegTreeMax(int n) {
sz = n;
seg.resize(4*n+5, -inf);
}
void upd(int node, int l, int r, int idx, int val) {
if(l>idx || r<idx) return;
if(l==r) {
seg[node] = max(seg[node], val);
return;
}
int mid = (l+r)>>1;
upd(node<<1, l, mid, idx, val); upd(node<<1|1, mid+1, r, idx, val);
seg[node] = max(seg[node<<1], seg[node<<1|1]);
}
int get(int node, int l, int r, int ql, int qr) {
if(l>qr || r<ql) return -inf;
if(ql<=l && r<=qr) return seg[node];
int mid = (l+r)>>1;
return max(get(node<<1, l, mid, ql, qr), get(node<<1|1, mid+1, r, ql, qr));
}
int walk(int node, int l, int r, int val) {
if(l==r) {
if(seg[node]>val) return l;
return -1;
}
int mid = (l+r)>>1;
if(seg[node<<1|1]>val) {
return walk(node<<1|1, mid+1, r, val);
} else if(seg[node<<1]>val) {
return walk(node<<1, l, mid, val);
} else {
return -1;
}
}
};
struct Item {
int x, y, z;
bool operator<(Item o) const {
return x<o.z;
}
} a[N];
int n, m, ans;
vector<int> v;
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
cin >> n;
v.pb(0);
for (int i=1; i<=n; i++) {
cin >> a[i].x >> a[i].y >> a[i].z;
v.pb(a[i].x); v.pb(a[i].y); v.pb(a[i].z);
}
sort(all(v));
v.erase(unique(all(v)), v.end());
for (int i=1; i<=n; i++) {
a[i].x = lower_bound(all(v), a[i].x)-v.begin();
a[i].y = lower_bound(all(v), a[i].y)-v.begin();
a[i].z = lower_bound(all(v), a[i].z)-v.begin();
}
sort(a+1, a+n+1);
m = sz(v)-1;
SegTreeMax s1(m), s2(m);
SegTreeMin s3(m);
int idx = 1;
for (int i=1; i<=n; i++) {
while (a[idx].x<a[i].x) {
s1.upd(1, 1, m, a[idx].y, a[idx].z);
s3.upd(1, 1, m, a[idx].y, a[idx].z);
int tmp = s1.get(1, 1, m, 1, a[idx].y-1);
if(tmp>a[idx].z) s2.upd(1, 1, m, a[idx].y, tmp);
tmp = s3.walk(1, 1, m, a[idx].z);
if(tmp!=-1) s2.upd(1, 1, m, tmp, a[idx].z);
idx++;
}
int tmp = s2.walk(1, 1, m, a[i].z);
if(tmp!=-1) ans = max(ans, v[a[i].x]+v[tmp]+v[s2.get(1, 1, m, tmp, m)]);
}
if(ans) cout << ans;
else cout << -1;
}
