#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define dbg(x) "[" #x " = " << (x) << "]"
const int MAX = 5e4 + 5;
const int base = 31;
const int mod = 1e9 + 9;
struct mint{
int v;
mint() : v(0) {}
mint(int v) : v(v) {}
mint& operator += (const mint& o){
v += o.v;
if(v >= mod) v -= mod;
return *this;
}
mint& operator -= (const mint& o){
v -= o.v;
if(v < 0) v += mod;
return *this;
}
mint& operator *= (const mint& o){
v = 1ll * v * o.v % mod;
return *this;
}
mint power(ll n) const{
mint res(1), base = *this;
for(; n > 0; n >>= 1, base *= base){
if(n & 1) res *= base;
}
return res;
}
mint inv() const{
return power(mod - 2);
}
mint& operator /= (const mint& o){ return *this *= o.inv(); }
friend mint operator + (mint a, const mint& b){ return a += b; }
friend mint operator - (mint a, const mint& b){ return a -= b; }
friend mint operator * (mint a, const mint& b){ return a *= b; }
friend mint operator / (mint a, const mint& b){ return a /= b; }
friend bool operator == (const mint& a, const mint& b){ return a.v == b.v; }
friend bool operator != (const mint& a, const mint& b){ return a.v != b.v; }
friend ostream& operator << (ostream& out, const mint& v){ return out << v.v; }
};
mint base_power[MAX], inv_base_power[MAX];
int N, c[MAX];
vector<int> adj[MAX];
int sz[MAX], checking;
bool deleted[MAX], result;
vector<tuple<mint, mint, int>> subtree[MAX];
int dfs_sz(int u, int p){
sz[u] = 1;
for(auto v : adj[u]) if(v != p && !deleted[v]){
sz[u] += dfs_sz(v, u);
}
return sz[u];
}
int find_centroid(int u, int p, int target){
for(auto v : adj[u]) if(v != p && !deleted[v] && sz[v] * 2 > target){
return find_centroid(v, u, target);
}
return u;
}
//the "hash" for string S (|S| = N) : h(S) = S[0] * base[N - 1] + S[1] * base[N - 2] + ... + S[N - 1]
void get_data(int u, int p, mint hash_c_to_u, mint hash_u_to_c, int dep, vector<tuple<mint, mint, int>>& receiver){
//cout << u << ' ' << hash_c_to_u << ' ' << hash_u_to_c << ' ' << dep << '\n';
receiver.emplace_back(hash_c_to_u, hash_u_to_c, dep);
for(auto v : adj[u]) if(v != p && !deleted[v] && dep + 1 <= checking){
mint hash_c_to_v = (hash_c_to_u * base) + c[v];
mint hash_v_to_c = hash_v_to_c + (c[v] * base_power[dep]);
get_data(v, u, hash_c_to_v, hash_v_to_c, dep + 1, receiver);
}
}
int mx = 0;
set<int> S[MAX];
void insert(int i, mint v){
//cout << "insert : " << i << ' ' << v << '\n';
mx = max(mx, i);
S[i].insert(v.v);
}
bool can(int i, mint v){
//cout << "find : " << i << ' ' << v << '\n';
return S[i].count(v.v);
}
void decompose(int u){
u = find_centroid(u, -1, dfs_sz(u, -1));
deleted[u] = true;
mx = 0;
for(auto v : adj[u]) if(!deleted[v]){
subtree[v].clear();
get_data(v, u, c[v], c[v], 1, subtree[v]);
for(auto [hash_v_to_u, hash_u_to_v, len] : subtree[v]){
mint hash_c_to_u = hash_v_to_u + c[u] * base_power[len];
mint hash_u_to_c = (hash_u_to_v * base) + c[u];
if(len + 1 == checking && hash_c_to_u == hash_u_to_c) {
result = true;
return;
}
mint target = (hash_u_to_c * base_power[checking - len - 1]) - hash_v_to_u;
if(can(checking - len - 1, target)) {
result = true;
return;
}
}
for(auto [hash_v_to_u, hash_u_to_v, len] : subtree[v]){
mint hash_u_to_c = (hash_u_to_v * base) + c[u];
mint target = (hash_u_to_c * base_power[checking - len - 1]) - hash_v_to_u;
insert(len, target);
}
subtree[v].clear();
}
for(int i = 0; i <= mx; ++i){
S[i].clear();
}
for(auto v : adj[u]) if(!deleted[v]){
decompose(v);
if(result) return;
}
}
bool check(int x){
checking = x;
for(int i = 0; i <= N; ++i){
sz[i] = 0;
deleted[i] = 0;
S[i].clear();
subtree[i].clear();
}
result = false;
decompose(1);
return result;
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0); srand(time(nullptr));
#ifdef LOCAL
freopen("task.inp", "r", stdin);
freopen("task.out", "w", stdout);
#endif // LOCAL
cin >> N;
for(int i = 1; i <= N; ++i){
char ch; cin >> ch;
c[i] = ch - 'a' + 1;
}
base_power[0] = 1; inv_base_power[0] = 1;
for(int i = 1; i <= N; ++i) base_power[i] = base_power[i - 1] * base;
inv_base_power[N] = base_power[N].inv();
for(int i = N - 1; i >= 1; --i){
inv_base_power[i] = inv_base_power[i + 1] * base;
}
for(int i = 1; i < N; ++i){
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
int ans = 1;
//odd -> 2l + 1
int lo = 1, hi = (N - 1) / 2;
while(lo <= hi){
int mid = lo + hi >> 1;
if(check(2 * mid + 1)) ans = max(ans, 2 * mid + 1), lo = mid + 1;
else hi = mid - 1;
}
lo = 1, hi = N / 2;
while(lo <= hi){
int mid = lo + hi >> 1;
if(check(2 * mid)) ans = max(ans, 2 * mid), lo = mid + 1;
else hi = mid - 1;
}
cout << ans << '\n';
return 0;
}
