#define _USE_MATH_DEFINES #include using namespace std; #define FOR(i,m,n) for(int i=(m);i<(n);++i) #define REP(i,n) FOR(i,0,n) #define ALL(v) (v).begin(),(v).end() using ll = long long; constexpr int INF = 0x3f3f3f3f; constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL; constexpr double EPS = 1e-8; constexpr int MOD = 1000000007; // constexpr int MOD = 998244353; constexpr int dy[] = {1, 0, -1, 0}, dx[] = {0, -1, 0, 1}; constexpr int dy8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dx8[] = {0, -1, -1, -1, 0, 1, 1, 1}; template inline bool chmax(T &a, U b) { return a < b ? (a = b, true) : false; } template inline bool chmin(T &a, U b) { return a > b ? (a = b, true) : false; } struct IOSetup { IOSetup() { std::cin.tie(nullptr); std::ios_base::sync_with_stdio(false); std::cout << fixed << setprecision(20); } } iosetup; template struct Edge { int src, dst; CostType cost; Edge(int src, int dst, CostType cost = 0) : src(src), dst(dst), cost(cost) {} inline bool operator<(const Edge &x) const { return cost != x.cost ? cost < x.cost : dst != x.dst ? dst < x.dst : src < x.src; } inline bool operator<=(const Edge &x) const { return !(x < *this); } inline bool operator>(const Edge &x) const { return x < *this; } inline bool operator>=(const Edge &x) const { return !(*this < x); } }; int main() { int n; string s; cin >> n >> s; int m = s.length(); string t = s; reverse(ALL(t)); vector>> graph(n); REP(_, n - 1) { int u, v; char c; cin >> u >> v >> c; --u; --v; graph[u].emplace_back(u, v, c); graph[v].emplace_back(v, u, c); } int ans = 0; vector dp1(n, vector(m + 1, 0)), dp2(n, vector(m + 1, 0)); auto f = [&](auto &&f, int par, int ver) -> void { for (const Edge &e : graph[ver]) { if (e.dst == par) continue; f(f, ver, e.dst); vector child1(m + 1, -INF), child2(m + 1, -INF); REP(i, m + 1) { chmax(child1[i], dp1[e.dst][i]); chmax(child2[i], dp2[e.dst][i]); if (i + 1 <= m) { chmax(child1[i + 1], child1[i] + (e.cost == s[i])); chmax(child2[i + 1], child2[i] + (e.cost == t[i])); } } REP(i, m + 1) { chmax(ans, dp1[ver][i] + child2[m - i]); chmax(ans, dp2[ver][i] + child1[m - i]); chmax(dp1[ver][i], child1[i]); chmax(dp2[ver][i], child2[i]); } } }; f(f, -1, 0); cout << ans << '\n'; return 0; }