#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace std;
using namespace __gnu_pbds;
#define endl "\n"
#define ll long long
#define IOS ios_base::sync_with_stdio(false); cin.tie(nullptr);
const int N = 5e4 + 5;
const long long M = 1e9 + 7;
const long long P = 26, INV_P = 576923081;
const long long Q = 53, INV_Q = 56603774;
struct chash {
long long operator()(pair<long long, long long> x) const { return x.first* M + x.second; }
};
pair<long long, long long> single(char a) {
return make_pair(a - 'a' + 1, a - 'a' + 1);
}
pair<long long, long long> mul(pair<long long, long long> a, pair<long long, long long> b) {
return make_pair(a.first * b.first % M, a.second * b.second % M);
}
pair<long long, long long> sub(pair<long long, long long> a, pair<long long, long long> b) {
return make_pair((a.first - b.first + M) % M, (a.second - b.second + M) % M);
}
pair<long long, long long> add(pair<long long, long long> a, pair<long long, long long> b) {
return make_pair((a.first + b.first + M) % M, (a.second + b.second + M) % M);
}
string s;
int sz[N];
bool seen_c[N];
int parent_c[N];
int depth[N];
long long pw_p[N], pw_q[N];
long long inv_p[N], inv_q[N];
vector<int> adj[N];
pair<long long, long long> rising[N], falling[N];
gp_hash_table<pair<long long, long long>, int, chash> mp;
int ans = 1;
bool found = false;
vector<int> stk;
void dfs_subtree(int u, int p) {
sz[u] = 1;
for (int v : adj[u]) {
if (v != p && !seen_c[v]) {
dfs_subtree(v, u);
sz[u] += sz[v];
}
}
return;
}
int dfs_centroid(int u, int p, int n) {
for (int v : adj[u]) {
if (v != p && !seen_c[v] && sz[v] > n / 2) {
return dfs_centroid(v, u, n);
}
}
return u;
}
void dfs1(int u, int p) {
if (found) {
return;
}
rising[u] = add(rising[p], mul(single(s[u]), make_pair(pw_p[depth[u]], pw_q[depth[u]])));
falling[u] = add(mul(falling[p], make_pair(P, Q)), single(s[u]));
for (int v : adj[u]) {
if (v != p && !seen_c[v]) {
depth[v] = depth[u] + 1;
dfs1(v, u);
}
}
return;
}
void dfs2(int u, int p, int k) {
if (found) {
return;
}
stk.push_back(u);
if (depth[u] + 1 == k) {
if (rising[u] == falling[u]) {
found = true;
}
} else if (depth[u] + 1 < k) {
int anc = k - (depth[u] + 1);
if (anc <= depth[u]) {
anc = stk[depth[u] - anc];
if (rising[anc] == falling[anc]) {
pair<long long, long long> h = mul(sub(rising[u], rising[anc]), make_pair(inv_p[depth[anc] + 1], inv_q[depth[anc] + 1]));
auto it = mp.find(h);
if (it != mp.end() && it->second > 0) {
found = true;
}
}
}
}
for (int v : adj[u]) {
if (v != p && !seen_c[v]) {
dfs2(v, u, k);
}
}
stk.pop_back();
return;
}
void dfs3(int u, int p, int c, int add) {
if (found) {
return;
}
mp[mul(sub(rising[u], rising[c]), make_pair(INV_P, INV_Q))] += add;
for (int v : adj[u]) {
if (v != p && !seen_c[v]) {
dfs3(v, u, c, add);
}
}
return;
}
void build(int u, int p, int n, int k) {
if (found) {
return;
}
dfs_subtree(u, u);
int c = dfs_centroid(u, u, sz[u]);
if (p == -1) {
p = c;
}
parent_c[c] = p;
seen_c[c] = true;
stk.push_back(c);
rising[c] = make_pair(s[c] - 'a' + 1, s[c] - 'a' + 1);
falling[c] = rising[c];
depth[c] = 0;
for (int v : adj[c]) {
if (!seen_c[v]) {
depth[v] = 1;
dfs1(v, c);
dfs3(v, c, c, 1);
}
}
for (int v : adj[c]) {
if (!seen_c[v]) {
dfs3(v, c, c, -1);
dfs2(v, c, k);
dfs3(v, c, c, 1);
}
}
mp.clear();
stk.pop_back();
for (int v : adj[c]) {
if (!seen_c[v]) {
build(v, c, n, k);
}
}
return;
}
int main() {
IOS;
int n;
cin >> n >> s;
pw_p[0] = 1, pw_q[0] = 1;
inv_p[0] = 1, inv_q[0] = 1;
for (int i = 1; i < n; i++) {
pw_p[i] = pw_p[i - 1] * P % M;
pw_q[i] = pw_q[i - 1] * Q % M;
inv_p[i] = inv_p[i - 1] * INV_P % M;
inv_q[i] = inv_q[i - 1] * INV_Q % M;
}
for (int i = 0; i < n - 1; i++) {
int u, v;
cin >> u >> v;
u--, v--;
adj[u].push_back(v);
adj[v].push_back(u);
}
int l = 0, r = n / 2;
while (l <= r) {
found = false;
int mid = (l + r) / 2;
build(0, -1, n, 2 * mid + 1);
for (int i = 0; i < n; i++) {
seen_c[i] = false;
}
stk.clear();
if (found) {
ans = max(ans, 2 * mid + 1);
l = mid + 1;
} else {
r = mid - 1;
}
}
l = 1, r = n / 2;
while (l <= r) {
found = false;
int mid = (l + r) / 2;
build(0, -1, n, 2 * mid);
for (int i = 0; i < n; i++) {
seen_c[i] = false;
}
stk.clear();
if (found) {
ans = max(ans, 2 * mid);
l = mid + 1;
} else {
r = mid - 1;
}
}
cout << ans;
return 0;
}
