#pragma GCC target("avx2") #pragma GCC optimize("Ofast") #pragma GCC optimize("unroll-loops") #include //#include using namespace std; //using namespace atcoder; #define DEBUG #ifdef DEBUG template ostream &operator<<(ostream &os, const pair &p) { os << '(' << p.first << ',' << p.second << ')'; return os; } template ostream &operator<<(ostream &os, const vector &v) { os << '{'; for(int i = 0; i < (int)v.size(); i++) { if(i) { os << ','; } os << v[i]; } os << '}'; return os; } void debugg() { cerr << endl; } template void debugg(const T &x, const Args &... args) { cerr << " " << x; debugg(args...); } #define debug(...) \ cerr << __LINE__ << " [" << #__VA_ARGS__ << "]: ", debugg(__VA_ARGS__) #define dump(x) cerr << __LINE__ << " " << #x << " = " << (x) << endl #else #define debug(...) (void(0)) #define dump(x) (void(0)) #endif using namespace std; typedef long long ll; typedef vector vl; typedef vector> vvl; typedef vector vc; typedef vector vs; typedef vector vb; typedef vector vd; typedef pair P; typedef pair pii; typedef vector

vpl; typedef tuple tapu; #define rep(i,n) for(int i=0; i<(n); i++) #define REP(i,a,b) for(int i=(a); i<(b); i++) #define all(x) (x).begin(), (x).end() #define rall(x) (x).rbegin(), (x).rend() const int inf = (1<<30) - 1; const ll linf = 1LL<<61; const int MAX = 510000; int dy[8] = {0,1,0,-1,1,-1,-1,1}; int dx[8] = {-1,0,1,0,1,-1,1,-1}; const double pi = 3.14159265358979; const double eps = 1e-8; template inline bool chmin(T1 &a,T2 b){ if(a>b){ a = b; return true; } else return false; } template inline bool chmax(T1 &a,T2 b){ if(a<=b){ a = b; return true; } else return false; } template inline void print(T &a){ int sz = a.size(); for(auto itr = a.begin(); itr != a.end(); itr++){ cout << *itr; sz--; if(sz) cout << " "; } cout << "\n"; } template inline void print2(T1 a, T2 b){ cout << a << " " << b << "\n"; } template inline void print3(T1 a, T2 b, T3 c){ cout << a << " " << b << " " << c << "\n"; } void mark() {cout << "#" << "\n";} ll pcount(ll x) {return __builtin_popcountll(x);} const int mod = 1e9 + 7; //const int mod = 998244353; int dp[2020][2020]; int ep[2020][2020]; int main(){ int n; cin >> n; string s; cin >> s; vector>> G(n); rep(i,n-1){ int u,v; char c; cin >> u >> v >> c; u--; v--; G[u].emplace_back(v,c); G[v].emplace_back(u,c); } int m = s.size(); int ans = 0; auto dfs = [&](auto &&dfs, int u, int p) -> void { vector> d1(m+1,{0,-1}), d2(m+1,{0,-1}); for(auto v : G[u]){ if(v.first == p) continue; dfs(dfs,v.first,u); rep(i,m){ int C = s[i] == v.second; if(dp[v.first][i] + C >= d1[i].first){ d2[i] = d1[i]; d1[i] = {dp[v.first][i] + C, v.first}; }else if(dp[v.first][i] + C >= d2[i].first){ d2[i] = {dp[v.first][i] + C, v.first}; } chmax(dp[u][i+1], dp[v.first][i] + C); chmax(ep[u][i], ep[v.first][i+1] + C); } } for(auto v : G[u]){ if(v.first == p) continue; rep(i,m-1){ int C = s[i+1] == v.second; if(d1[i].second == v.first) chmax(ans, d2[i].first + ep[v.first][i+2] + C); else chmax(ans, d1[i].first + ep[v.first][i+2] + C); } } rep(i,m) chmax(dp[u][i+1], dp[u][i]); for(int i=m-1; i>=0; i--) chmax(ep[u][i], ep[u][i+1]); chmax(ans, dp[u][m]); chmax(ans, ep[u][0]); }; dfs(dfs,0,-1); cout << ans << endl; }