// >>> TEMPLATES #include using namespace std; using ll = long long; using ld = long double; using i32 = int32_t; using i64 = int64_t; using u32 = uint32_t; using u64 = uint64_t; #define int ll #define rep(i, n) for (int i = 0; i < (int)(n); i++) #define rep1(i, n) for (int i = 1; i <= (int)(n); i++) #define repR(i, n) for (int i = (int)(n)-1; i >= 0; i--) #define rep1R(i, n) for (int i = (int)(n); i >= 1; i--) #define loop(i, a, B) for (int i = a; i B; i++) #define loopR(i, a, B) for (int i = a; i B; i--) #define all(x) begin(x), end(x) #define allR(x) rbegin(x), rend(x) #define rng(x, l, r) begin(x) + (l), begin(x) + (r) #define pb push_back #define eb emplace_back #define fst first #define snd second template constexpr auto mp(A &&a, B &&b) { return make_pair(forward(a), forward(b)); } template constexpr auto mt(T&&... x) { return make_tuple(forward(x)...); } template auto constexpr inf_ = numeric_limits::max()/2-1; auto constexpr INF32 = inf_; auto constexpr INF64 = inf_; auto constexpr INF = inf_; #ifdef LOCAL #include "debug.hpp" #else #define dump(...) (void)(0) #define say(x) (void)(0) #define debug if (0) #endif template struct pque : priority_queue, Comp> { vector &data() { return this->c; } void clear() { this->c.clear(); } }; template using pque_max = pque>; template using pque_min = pque>; template ::value, int> = 0> ostream& operator<<(ostream& os, T const& a) { bool f = true; for (auto const& x : a) os << (f ? "" : " ") << x, f = false; return os; } template ::value, int> = 0> ostream& operator<<(ostream& os, const T (&a)[N]) { bool f = true; for (auto const& x : a) os << (f ? "" : " ") << x, f = false; return os; } template ())), class = typename enable_if::value>::type> istream& operator>>(istream& is, T &a) { for (auto& x : a) is >> x; return is; } template ostream& operator<<(ostream& os, pair const& p) { return os << p.first << " " << p.second; } template istream& operator>>(istream& is, pair& p) { return is >> p.first >> p.second; } struct IOSetup { IOSetup() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(15); } } iosetup; template struct FixPoint : private F { constexpr FixPoint(F&& f) : F(forward(f)) {} template constexpr auto operator()(T&&... x) const { return F::operator()(*this, forward(x)...); } }; struct MakeFixPoint { template constexpr auto operator|(F&& f) const { return FixPoint(forward(f)); } }; #define MFP MakeFixPoint()| #define def(name, ...) auto name = MFP [&](auto &&name, __VA_ARGS__) template struct vec_impl { using type = vector::type>; template static type make_v(size_t n, U&&... x) { return type(n, vec_impl::make_v(forward(x)...)); } }; template struct vec_impl { using type = T; static type make_v(T const& x = {}) { return x; } }; template using vec = typename vec_impl::type; template auto make_v(Args&&... args) { return vec_impl::make_v(forward(args)...); } template void quit(T const& x) { cout << x << endl; exit(0); } template constexpr bool chmin(T& x, U const& y) { if (x > y) { x = y; return true; } return false; } template constexpr bool chmax(T& x, U const& y) { if (x < y) { x = y; return true; } return false; } template constexpr auto sumof(It b, It e) { return accumulate(b, e, typename iterator_traits::value_type{}); } template int sz(T const& x) { return x.size(); } template int lbd(C const& v, T const& x) { return lower_bound(begin(v), end(v), x)-begin(v); } template int ubd(C const& v, T const& x) { return upper_bound(begin(v), end(v), x)-begin(v); } constexpr int64_t mod(int64_t x, int64_t m) { assert(m > 0); return (x %= m) < 0 ? x+m : x; } constexpr int64_t div_floor(int64_t x, int64_t y) { assert(y != 0); return x/y - ((x^y) < 0 and x%y); } constexpr int64_t div_ceil(int64_t x, int64_t y) { assert(y != 0); return x/y + ((x^y) > 0 and x%y); } constexpr int dx[] = { 1, 0, -1, 0, 1, -1, -1, 1 }; constexpr int dy[] = { 0, 1, 0, -1, 1, 1, -1, -1 }; constexpr int popcnt(ll x) { return __builtin_popcountll(x); } mt19937_64 seed_{random_device{}()}; template Int rand(Int a, Int b) { return uniform_int_distribution(a, b)(seed_); } i64 irand(i64 a, i64 b) { return rand(a, b); } // [a, b] u64 urand(u64 a, u64 b) { return rand(a, b); } // template void shuffle(It l, It r) { shuffle(l, r, seed_); } vector &operator--(vector &v) { for (int &x : v) --x; return v; } vector &operator++(vector &v) { for (int &x : v) ++x; return v; } // <<< // >>> re-rooting // >>> edge info #ifndef EDGE_INFO #define EDGE_INFO constexpr int dest(int v) { return v; } template ().to)> constexpr int dest(E const& e) { return e.to; } constexpr int cost(int) { return 1; } template ().cost)> constexpr auto cost(E const& e) { return e.cost; } template using cost_t = decltype(cost(declval())); #endif // <<< template struct ReRooting { vector> const* g; Monoid unit; Merge merge; // (Monoid, Monoid) -> Monoid AddEdge lift; // (Monoid, Edge) -> Monoid AddVertex add_vertex; // (Monoid, int vertex) -> Monoid vector dp_sub, dp_par, dp_all; ReRooting(vector> const& g, Monoid unit, Merge merge, AddEdge lift, AddVertex add_vertex) : g(&g), unit(unit), merge(merge), lift(lift), add_vertex(add_vertex), dp_sub(g.size(), unit), dp_par(g.size(), unit), dp_all(g.size(), unit) {} vector run() { assert(g->size()); dfs1(0, -1); dfs2(0, -1); dump(dp_sub); // lifted dump(dp_par); // lifted dump(dp_all); return dp_all; } void dfs1(int x, int p) { Monoid val = unit; for (auto const& e : (*g)[x]) { const int y = dest(e); if (y == p) continue; dfs1(y, x); val = merge(val, lift(dp_sub[y], e)); } dp_sub[x] = add_vertex(val, x); } void dfs2(int x, int p) { auto const& es = (*g)[x]; auto d = [&](int i) { return dest(es[i]); }; auto val = [&](int i) -> Monoid& { return d(i) == p ? dp_par[x] : dp_sub[d(i)]; }; const int m = es.size(); for (int i = 0; i < m; ++i) val(i) = lift(val(i), es[i]); { vector ldp(m+1, unit), rdp(m+1, unit); for (int i = 0; i < m; i++) ldp[i+1] = merge(ldp[i], val(i)); for (int i = m-1; i >= 0; i--) rdp[i] = merge(rdp[i+1], val(i)); dp_all[x] = add_vertex(rdp[0], x); for (int i = 0; i < m; i++) { if (d(i) == p) continue; dp_par[d(i)] = add_vertex(merge(ldp[i], rdp[i+1]), x); } } for (int i = 0; i < m; i++) if (d(i) != p) dfs2(d(i), x); } }; // <<< int32_t main() { int n; cin >> n; string s; cin >> s; struct edge { int to; char c; }; vector> g(n); rep (i, n-1) { int x, y; cin >> x >> y; --x, --y; char c; cin >> c; g[x].pb({y, c}); g[y].pb({x, c}); } vector unit(s.size() + 1); auto merge = [&](vector a, vector const& b) { rep (i, a.size()) chmax(a[i], b[i]); return a; }; auto lift = [&](vector const& a, edge const& e) { vector ret(s.size() + 1); repR (i, s.size()) { if (s[i] == e.c) chmax(ret[i], a[i+1] + 1); chmax(ret[i], a[i]); chmax(ret[i], ret[i+1]); } return ret; }; auto add_vertex = [&](vector const& a, int) { return a; }; auto rr = ReRooting(g, unit, merge, lift, add_vertex); auto dp = rr.run(); int ma = 0; rep (i, dp.size()) chmax(ma, *max_element(all(dp[i]))); cout << ma << '\n'; }