// In the name of Allah
#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef complex<ld> cld;
#define all(x) (x).begin(),(x).end()
#define len(x) ((ll) (x).size())
#define F first
#define S second
#define pb push_back
#define sep ' '
#define endl '\n'
#define Mp make_pair
#define kill(x) cout << x << '\n', exit(0)
#define set_dec(x) cout << fixed << setprecision(x);
#define file_io(x,y) freopen(x, "r", stdin); freopen(y, "w", stdout);
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
const int maxn = (1 << 19) + 4;
const int oo = 1e9 + 4;
struct node {
int res, max, min;
};
int n; pair<int, pii> A[maxn];
vector<int> arr; set<pii> st;
int tx[2][maxn]; node t[2 * maxn], null;
node f(node a, node b) {
node res;
res.res = max(a.res, b.res);
res.max = max(a.max, b.max);
res.min = min(a.min, b.min);
return res;
}
void build(int v, int tl, int tr) {
if (tr - tl == 1) {
t[v] = null;
return ;
}
int mid = (tl + tr) / 2;
build(2 * v + 1, tl, mid); build(2 * v + 2, mid, tr);
t[v] = f(t[2 * v + 1], t[2 * v + 2]);
}
void set_val(int v, int tl, int tr, int i, int x) {
if (i >= tr || i < tl) return ;
if (tr - tl == 1) {
t[v].res = arr[tl] + x;
t[v].max = x; t[v].min = x;
return ;
}
int mid = (tl + tr) / 2;
if (i < mid) set_val(2 * v + 1, tl, mid, i, x);
else set_val(2 * v + 2, mid, tr, i, x);
t[v] = f(t[2 * v + 1], t[2 * v + 2]);
}
void del_val(int v, int tl, int tr, int i) {
if (i >= tr || i < tl) return ;
if (tr - tl == 1) {
t[v] = null;
return ;
}
int mid = (tl + tr) / 2;
if (i < mid) del_val(2 * v + 1, tl, mid, i);
else del_val(2 * v + 2, mid, tr, i);
t[v] = f(t[2 * v + 1], t[2 * v + 2]);
}
int get_res(int v, int tl, int tr, int l, int x) {
l = max(l, tl);
if (l >= tr || t[v].max < x) return -oo;
if (l == tl && t[v].min >= x) return t[v].res;
int mid = (tl + tr) / 2;
return max(get_res(2 * v + 1, tl, mid, l, x), get_res(2 * v + 2, mid, tr, l, x));
}
int GI(int x) {
return lower_bound(all(arr), x) - arr.begin();
}
void set_mx(int I, int i, int x) {
for (++i; i < maxn; i += (i & -i)) tx[I][i] = max(tx[I][i], x);
}
int get_mx(int I, int i) {
int res = 0;
for (++i; i > 0; i -= (i & -i)) res = max(res, tx[I][i]);
return res;
}
void addp(int A1, int A2) {
auto it = st.lower_bound(Mp(A1, -1));
if (it != st.end()) {
auto f = *it;
if (f.F >= A1 && f.S >= A2) return ;
}
it = st.upper_bound(Mp(A1, oo));
while (true) {
if (it == st.begin()) break;
it--; auto f = *it;
if (f.S <= A2) {
st.erase(f); del_val(0, 0, len(arr), GI(f.F));
}
else break;
it = st.upper_bound(Mp(A1, oo));
}
st.insert(Mp(A1, A2)); set_val(0, 0, len(arr), GI(A1), A2);
}
void addx(int i) {
int j1 = GI(A[i].S.F), j2 = GI(A[i].S.S);
int valx = get_mx(0, j1 - 1); set_mx(0, j1, A[i].S.S);
if (valx > A[i].S.S) addp(A[i].S.F, valx);
valx = get_mx(1, j2 - 1); set_mx(1, j2, A[i].S.F);
if (valx > A[i].S.F) addp(valx, A[i].S.S);
}
void solve() {
cin >> n;
for (int i = 0; i < n; i++) {
cin >> A[i].F >> A[i].S.F >> A[i].S.S;
arr.pb(A[i].F); arr.pb(A[i].S.F); arr.pb(A[i].S.S);
}
sort(A, A + n); sort(all(arr)); arr.resize(unique(all(arr)) - arr.begin());
int ans = 0, j = 0;
build(0, 0, len(arr));
for (int i = 0; i < n; i++) {
if (A[i].F != A[j].F) {
for (int R = j; R < i; R++) addx(R);
j = i;
}
ans = max(ans, A[i].F + get_res(0, 0, len(arr), GI(A[i].S.F) + 1, A[i].S.S + 1));
}
if (ans == 0) cout << -1 << endl;
else cout << ans << endl;
}
int main() {
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
null.res = -oo; null.max = -oo; null.min = oo;
int T = 1;
while (T--) {
solve();
}
return 0;
}
