// clang-format off #include using namespace std; using uint = unsigned int; using ll = long long; using ull = unsigned long long; using pii = pair; using pll = pair; template using vec = vector; template using vvec = vector>; #define rep(i, n) for (int i = 0; i < (n); i++) #define rrep(i, n) for (int i = int(n) - 1; i >= 0; i--) #define all(x) begin(x), end(x) constexpr char ln = '\n'; template inline int SZ(const Container& v) { return int(v.size()); } template inline void UNIQUE(vector& v) { v.erase(unique(v.begin(), v.end()), v.end()); } template inline bool chmax(T1& a, T2 b) { if (a < b) { a = b; return true; } return false; } template inline bool chmin(T1& a, T2 b) { if (a > b) { a = b; return true; } return false; } inline int topbit(ull x) { return x == 0 ? -1 : 63 - __builtin_clzll(x); } inline int botbit(ull x) { return x == 0 ? 64 : __builtin_ctzll(x); } inline int popcount(ull x) { return __builtin_popcountll(x); } inline int kthbit(ull x, int k) { return (x >> k) & 1; } inline constexpr long long TEN(int x) { return x == 0 ? 1 : TEN(x - 1) * 10; } const string YESNO[2] = {"NO", "YES"}; const string YesNo[2] = {"No", "Yes"}; inline void YES(bool t = true) { cout << YESNO[t] << "\n"; } inline void Yes(bool t = true) { cout << YesNo[t] << "\n"; } template inline void drop(T x) { cout << x << "\n"; exit(0); } inline void print() { cout << "\n"; } template inline void print(const vector& v) { for (auto it = v.begin(); it != v.end(); ++it) { if (it != v.begin()) { cout << " "; } cout << *it; } print(); } template inline void print(const T& x, const Args& ... args) { cout << x << " "; print(args...); } #ifdef MINATO_LOCAL template ostream& operator<<(ostream& os, pair p) { return os << "(" << p.first << ", " << p.second << ")"; } template void debug_tuple(ostream& os, TUPLE _) { (void)os; (void)_; } template void debug_tuple(ostream &os, TUPLE t) { os << (N == 0 ? "" : ", ") << get(t); debug_tuple(os, t); } template ostream& operator<<(ostream& os, tuple t) { os << "("; debug_tuple<0, tuple, Args...>(os, t); return os << ")"; } string debug_delim(int& i) { return i++ == 0 ? "" : ", "; } #define debug_embrace(x) { int i = 0; os << "{"; { x } return os << "}"; } template ostream& operator<<(ostream& os, vector v) { debug_embrace( for (T e : v) { os << debug_delim(i) << e; } ) } template ostream& operator<<(ostream& os, array a) { debug_embrace( for (T e : a) { os << debug_delim(i) << e; } ) } template enable_if_t>, ostream>& operator<<(ostream& os, T(&a)[N]) { debug_embrace( for (T e : a) { os << debug_delim(i) << e; } ) } template ostream& operator<<(ostream& os, set s) { debug_embrace( for (Key e : s) { os << debug_delim(i) << e; }) } template ostream& operator<<(ostream& os, map mp) { debug_embrace( for (auto e : mp) { os << debug_delim(i) << e; }) } template ostream& operator<<(ostream& os, multiset s) { debug_embrace( for (Key e : s) { os << debug_delim(i) << e; }) } template ostream& operator<<(ostream& os, queue q) { debug_embrace( for (; !q.empty(); q.pop()) { os << debug_delim(i) << q.front(); } ) } template ostream& operator<<(ostream& os, deque q) { debug_embrace( for (T e : q) { os << debug_delim(i) << e; } ) } template ostream& operator<<(ostream& os, priority_queue q) { debug_embrace( for (; !q.empty(); q.pop()) { os << debug_delim(i) << q.top(); } ) } template ostream& operator<<(ostream& os, priority_queue, greater> q) { debug_embrace( for (; !q.empty(); q.pop()) { os << debug_delim(i) << q.top(); } ) } void debug_out() { cerr << endl; } template void debug_out(const T& x, const Args& ... args) { cerr << " " << x; debug_out(args...); } #define debug(...) cerr << __LINE__ << " : [" << #__VA_ARGS__ << "] =", debug_out(__VA_ARGS__) #else #define debug(...) (void(0)) #endif struct fast_ios { fast_ios() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); cerr << fixed << setprecision(7); }; } fast_ios_; /////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// // clang-format on struct HeavyLightDecomposition { vector> g; HeavyLightDecomposition(int n) : g(n), n_(n), vid(n, -1), head(n), sub(n, 1), par(n, -1), dep(n, 0), inv(n), type(n) {} int size() const { return n_; } void add_edge(int u, int v) { g[u].emplace_back(v); g[v].emplace_back(u); } void build(vector rs = {0}) { int c = 0, pos = 0; for (int r : rs) { dfs_sz(r); head[r] = r; dfs_hld(r, c++, pos); } } int operator[](int v) const { assert(0 <= v and v < n_); return vid[v]; } int depth(int v) const { assert(0 <= v and v < n_); return dep[v]; } int subtree_size(int v) const { assert(0 <= v and v < n_); return sub[v]; } int parent(int v) const { assert(0 <= v and v < n_); return par[v]; } int kth_ancestor(int v, int k) const { assert(0 <= v and v < n_); return kth_ancestor_(v, k); } int level_ancestor(int v, int d) const { assert(0 <= v and v < n_); return kth_ancestor_(v, dep[v] - d); } int lca(int u, int v) const { assert(0 <= u and u < n_); assert(0 <= v and v < n_); return lca_(u, v); } int distance(int u, int v) const { assert(0 <= u and u < n_); assert(0 <= v and v < n_); int w = lca_(u, v); return distance_(u, v, w); } int distance(int u, int v, int w) const { assert(0 <= u and u < n_); assert(0 <= v and v < n_); assert(0 <= w and w < n_); return distance_(u, v, w); } int cut_size(int u, int v) const { assert(0 <= u and u < n_); assert(0 <= v and v < n_); if (par[u] == v) return sub[u]; if (par[v] == u) return n_ - sub[v]; return -1; } int jump(int u, int v, int d) const { assert(0 <= u and u < n_); assert(0 <= v and v < n_); return jump_(u, v, d); } int step(int u, int v) const { assert(0 <= u and u < n_); assert(0 <= v and v < n_); return jump_(u, v, 1); } int meet(int u, int v, int w) const { assert(0 <= u and u < n_); assert(0 <= v and v < n_); assert(0 <= w and w < n_); comparator_in(u, v); comparator_in(v, w); comparator_in(u, v); int a = lca_(u, v); int b = lca_(v, w); if (dep[a] < dep[b]) return b; return a; } vector path(int u, int v) const { assert(0 <= u and u < n_); assert(0 <= v and v < n_); int w = lca_(u, v); int L = distance_(u, v, w); vector ret(L + 1); int it = 0; while (u != w) { ret[it++] = u; u = par[u]; } it = L; while (v != w) { ret[it--] = v; v = par[v]; } ret[it] = w; return ret; } template void path_query_vertex(int u, int v, const F& f) const { assert(0 <= u and u < n_); assert(0 <= v and v < n_); while (true) { comparator_in(u, v); f(max(vid[head[v]], vid[u]), vid[v] + 1); if (head[u] != head[v]) v = par[head[v]]; else break; } } template void path_query_edge(int u, int v, const F& f) const { assert(0 <= u and u < n_); assert(0 <= v and v < n_); while (true) { comparator_in(u, v); if (head[u] != head[v]) { f(vid[head[v]], vid[v] + 1); v = par[head[v]]; } else { if (u != v) f(vid[u] + 1, vid[v] + 1); break; } } } template void subtree_query_vertex(int v, const F& f) const { assert(0 <= v and v < n_); f(vid[v], vid[v] + sub[v]); } template void subtree_query_edge(int v, const F& f) const { assert(0 <= v and v < n_); f(vid[v] + 1, vid[v] + sub[v]); } template T noncommutative_query_vertex(int u, int v, T e, const F& f, const M& op) const { assert(0 <= u and u < n_); assert(0 <= v and v < n_); int w = lca_(u, v); T resl = e, resr = e; while (true) { resl = op(resl, f(vid[u] + 1, max(vid[head[u]], vid[w]))); if (head[w] != head[u]) u = par[head[u]]; else break; } while (true) { if (head[w] != head[v]) { resr = op(f(vid[head[v]], vid[v] + 1), resr); v = par[head[v]]; } else { if (w != v) resr = op(f(vid[w] + 1, vid[v] + 1), resr); break; } } return op(resl, resr); } template T noncommutative_query_edge(int u, int v, T e, const F& f, const M& op) const { assert(0 <= u and u < n_); assert(0 <= v and v < n_); int w = lca_(u, v); T resl = e, resr = e; while (true) { if (head[w] != head[u]) { resl = op(resl, f(vid[u] + 1, vid[head[u]])); u = par[head[u]]; } else { if (w != u) resl = op(resl, f(vid[u] + 1, vid[w] + 1)); break; } } while (true) { if (head[w] != head[v]) { resr = op(f(vid[head[v]], vid[v] + 1), resr); v = par[head[v]]; } else { if (w != v) resr = op(f(vid[w] + 1, vid[v] + 1), resr); break; } } return op(resl, resr); } private: int n_; vector vid, head, sub, par, dep, inv, type; void dfs_sz(int v) { vector& es = g[v]; if (~par[v]) es.erase(find(es.begin(), es.end(), par[v])); for (int& u : es) { par[u] = v; dep[u] = dep[v] + 1; dfs_sz(u); sub[v] += sub[u]; if (sub[u] > sub[es[0]]) swap(u, es[0]); } } void dfs_hld(int v, int c, int& pos) { vid[v] = pos++; inv[vid[v]] = v; type[v] = c; for (int u : g[v]) { if (u == par[v]) continue; head[u] = (u == g[v][0] ? head[v] : u); dfs_hld(u, c, pos); } } void comparator_in(int& u, int& v) const { if (vid[u] > vid[v]) swap(u, v); } int kth_ancestor_(int v, int k) const { if (dep[v] < k or k < 0) return -1; while (true) { if (dep[v] - dep[head[v]] + 1 <= k) { k -= dep[v] - dep[head[v]] + 1; v = par[head[v]]; } else { return inv[vid[v] - k]; } } } int lca_(int u, int v) const { while (true) { comparator_in(u, v); if (head[u] == head[v]) return u; v = par[head[v]]; } } int distance_(int u, int v, int w) const { return dep[u] + dep[v] - 2 * dep[w]; } int jump_(int u, int v, int d) const { int w = lca_(u, v); int L = distance_(u, v, w); if (L < d) return -1; if (d <= distance_(u, w, w)) return kth_ancestor_(u, d); return kth_ancestor_(v, L - d); } }; using Tu = tuple; int main() { int N; cin >> N; if (N == 2) drop(0); HeavyLightDecomposition HLD(N); map dic; vec es; rep(i, N - 1) { int a, b, c; cin >> a >> b >> c; a--; b--; if (a > b) swap(a, b); HLD.add_edge(a, b); dic[pii(a, b)] = c; es.emplace_back(c, a, b); } HLD.build(); sort(all(es)); reverse(all(es)); int u = 0, v = 0; int mx = 0, mn = 1e9; int ans = 1e9; { auto [c, a, b] = es[0]; u = a; v = b; mx = c; mn = c; auto [d, e, f] = es[1]; ans = d; } for (int i = 1; i < N - 1; i++) { auto [c, a, b] = es[i]; int meet_a = HLD.meet(u, v, a); int meet_b = HLD.meet(u, v, b); debug(u, v, a, b, meet_a, meet_b); if (meet_a != u and meet_a != v and meet_a != a) break; if (meet_b != u and meet_b != v and meet_b != b) break; if (meet_a == u and meet_b == u) { int s = u; int t = (HLD.distance(u, a) > HLD.distance(u, b) ? a : b); while (s != t) { debug(s, t); int w = HLD.step(s, t); { int p = s; int q = w; if (p > q) swap(p, q); int cost = dic[pii(p, q)]; chmin(mn, cost); } s = w; } u = s; } else if (meet_a == v and meet_b == v) { int s = v; int t = (HLD.distance(v, a) > HLD.distance(v, b) ? a : b); while (s != t) { int w = HLD.step(s, t); { int p = s; int q = w; if (p > q) swap(p, q); int cost = dic[pii(p, q)]; chmin(mn, cost); } s = w; } v = s; } chmin(ans, max(mx - mn, i < N - 1 ? get<0>(es[i + 1]) : 0)); } cout << ans << ln; }