#include "bits/stdc++.h" #include #include #pragma GCC target("avx2") #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") #define ALL(x) (x).begin(), (x).end() #define RALL(x) (x).rbegin(), (x).rend() #define SZ(x) ((lint)(x).size()) #define FOR(i, begin, end) for(lint i=(begin),i##_end_=(end);i=i##_begin_;--i) #define REP(i, n) FOR(i,0,n) #define IREP(i, n) IFOR(i,0,n) #define endk '\n' using namespace std; typedef unsigned long long _ulong; typedef int lint; typedef long double ld; typedef pair plint; typedef pair pld; struct fast_ios { fast_ios() { cin.tie(nullptr), ios::sync_with_stdio(false), cout << fixed << setprecision(20); }; } fast_ios_; template auto add = [](T a, T b) -> T { return a + b; }; template auto f_max = [](T a, T b) -> T { return max(a, b); }; template auto f_min = [](T a, T b) -> T { return min(a, b); }; template using V = vector; using Vl = V; using VVl = V; template< typename T > ostream& operator<<(ostream& os, const vector< T >& v) { for (int i = 0; i < (int)v.size(); i++) os << v[i] << (i + 1 != v.size() ? " " : ""); return os; } template< typename T >istream& operator>>(istream& is, vector< T >& v) { for (T& in : v) is >> in; return is; } template bool chmax(T& a, const T& b) { if (a < b) { a = b; return 1; } return 0; } template bool chmin(T& a, const T& b) { if (b < a) { a = b; return 1; } return 0; } template T div_floor(T a, T b) { if (b < 0) a *= -1, b *= -1; return a >= 0 ? a / b : (a + 1) / b - 1; } template T div_ceil(T a, T b) { if (b < 0) a *= -1, b *= -1; return a > 0 ? (a - 1) / b + 1 : a / b; } template struct rec { F f; rec(F&& f_) : f(std::forward(f_)) {} template auto operator()(Args &&... args) const { return f(*this, std::forward(args)...); } }; lint gcd(lint a, lint b) { if (b == 0) return a; else return gcd(b, a % b); } lint digit(lint a) { return (lint)log10(a); } lint e_dist(plint a, plint b) { return abs(a.first - b.first) * abs(a.first - b.first) + abs(a.second - b.second) * abs(a.second - b.second); } lint m_dist(plint a, plint b) { return abs(a.first - b.first) + abs(a.second - b.second); } bool check_overflow(lint a, lint b, lint limit) { if (b == 0) return false; return a > limit / b; } // a * b > c => true void Worshall_Floyd(VVl& g) { REP(k, SZ(g)) REP(i, SZ(g)) REP(j, SZ(g)) chmin(g[i][j], g[i][k] + g[k][j]); } const lint MOD1000000007 = 1000000007, MOD998244353 = 998244353, INF = 1e9; lint dx[8] = { 0, -1, 0, 1, 1, -1, 1, -1 }, dy[8] = { -1, 0, 1, 0, -1, -1, 1, 1 }; bool YN(bool flag) { cout << (flag ? "YES" : "NO") << endk; return flag; } bool yn(bool flag) { cout << (flag ? "Yes" : "No") << endk; return flag; } struct Edge { lint from, to; lint cost; Edge() { } Edge(lint u, lint v, lint c) { cost = c; from = u; to = v; } bool operator<(const Edge& e) const { return cost < e.cost; } }; struct WeightedEdge { lint to; lint cost; WeightedEdge(lint v, lint c = 1) { to = v; cost = c; } bool operator<(const WeightedEdge& e) const { return cost < e.cost; } }; using WeightedGraph = V>; typedef pair tlint; typedef pair qlint; typedef pair valstr; lint N; int main() { cin >> N; string s; cin >> s; VVl poses(26); REP(i, SZ(s)) poses[s[i] - 'a'].push_back(i); V> to(N); REP(i, N - 1) { lint u, v; char c; cin >> u >> v >> c; u--; v--; to[u].push_back({ v, c }); to[v].push_back({ u, c }); } V dp(N); Vl tmp(SZ(s) + 1, -1); V> fx(N); REP(i, N) { dp[i].assign(SZ(to[i]), tmp); REP(j, SZ(to[i])) { fx[i][to[i][j].first] = j; } } auto dfs = [&](auto&& dfs, lint curr, lint prv, lint idx) -> lint { if (dp[curr][fx[curr][prv]][idx] != -1) return dp[curr][fx[curr][prv]][idx]; lint maxv = 0; for (auto nxt : to[curr]) { if (prv == nxt.first) continue; lint _c = nxt.second - 'a'; lint nxt_idx = lower_bound(ALL(poses[_c]), idx) - poses[_c].begin(); if (nxt_idx != SZ(poses[_c])) { chmax(maxv, dfs(dfs, nxt.first, curr, poses[_c][nxt_idx] + 1) + 1); } else { chmax(maxv, dfs(dfs, nxt.first, curr, idx)); } } return dp[curr][fx[curr][prv]][idx] = maxv; }; lint ans = 0; REP(i, N) { chmax(ans, dfs(dfs, i, -1, -1)); } cout << ans << endk; }