/**
* author: AgentPengin ( Độc cô cầu bại )
* created: 23.12.2022 10:08:02
* too lazy to update time
**/
#include<bits/stdc++.h>
#define EL '\n'
#define fi first
#define se second
#define NAME "TASK"
#define ll long long
#define lcm(a,b) (a/gcd(a,b))*b
#define db(val) "["#val" = " << (val) << "] "
#define bend(v) (v).begin(),(v).end()
#define sz(v) (int)(v).size()
#define ex exit(0)
using namespace std;
const ll mod = 1e9 + 7;
const int inf = 0x1FFFFFFF;
const int MAXN = 2e5 + 5;
const ll base = 35711;
int n,Len,valid[MAXN],child[MAXN],mx_depth;
char a[MAXN];
vector<int> adj[MAXN];
vector<pair<int,ll>> b;
ll po[MAXN];
unordered_map<ll,bool> f[MAXN];
void countChild(int u,int p) {
child[u] = 1;
for (auto v : adj[u]) {
if (v != p && valid[v]) {
countChild(v,u);
child[u] += child[v];
}
}
}
bool dfs(int u,int p,int h,ll hashdown,ll hashup) {
if (h > Len) return false;
if (p) {
hashdown = (hashdown * base + a[u]) % mod;
}
hashup = (hashup + 1LL * a[u] * po[h - 1]) % mod;
ll x = (hashup * po[Len - h] - hashdown + mod) % mod;
if (!p) f[h][x] = true;
if (f[Len - h + 1].find(x) != f[Len - h + 1].end()) return true;
for (auto v : adj[u]) {
if (v != p && valid[v]) {
if (!p) b.clear();
if (dfs(v,u,h + 1,hashdown,hashup)) return true;
if (!p) {
for (auto x : b) {
f[x.fi][x.se] = true;
}
}
}
}
mx_depth = max(mx_depth,h);
b.push_back({h,x});
return false;
}
bool solve(int u,int n) {
countChild(u,0);
int flag = 1,half = n / 2;
while(flag) {
flag = 0;
for (auto v : adj[u]) {
if (valid[v] && child[v] < child[u] && child[v] > half) {
u = v;
flag = true;
break;
}
}
}
countChild(u,0);
if (dfs(u,0,1,0,0)) return true;
for (int i = 1;i <= mx_depth;i++) f[i].clear();
mx_depth = 0;
valid[u] = false;
for (auto v : adj[u]) {
if (valid[v]) {
if (solve(v,child[v])) return true;
}
}
return false;
}
bool check(int len) {
Len = len;
for (int i = 1;i <= n;i++) {
valid[i] = 1;
f[i].clear();
}
return solve(1,n);
}
signed main() {
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
if (ifstream(NAME".inp")) {
freopen(NAME".inp","r",stdin);
freopen(NAME".out","w",stdout);
}
cin >> n;
for (int i = 1;i <= n;i++) cin >> a[i];
for (int i = 1;i < n;i++) {
int u,v; cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
po[0] = 1;
for (int i = 1;i <= n;i++) po[i] = po[i - 1] * base % mod;
int l = 0,r = (n - 1) / 2;
while(l < r) {
int mid = (l + r + 1) >> 1;
if (check(mid * 2 + 1)) {
l = mid;
} else {
r = mid - 1;
}
}
int ans = r * 2 + 1;
l = 0,r = n / 2;
while(l < r) {
int mid = (l + r + 1) >> 1;
if (check(mid * 2)) {
l = mid;
} else r = mid - 1;
}
cout << max(ans,r * 2);
cerr << "\nTime elapsed: " << 1000 * clock() / CLOCKS_PER_SEC << "ms\n";
return 0;
}
// agent pengin wants to take apio (with anya-san)
