#include <bits/stdc++.h>
#define int long long
#define pb push_back
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
#define pii pair<int,int>
#define INF 1e9
#define FOR(i, a, b) for(int i = a; i <= b; ++i)
#define FORD(i, a, b) for(int i = a; i >= b; --i)
#define TASK "test"
using namespace std;
const int N = 50005;
const int mod = 1e9 + 7;
const int base = 311;
int n, si[N], pw[N], mx = 0, curCen;
bool vis[N];
char s[N];
vector<int> g[N];
vector<pii> st;
map<int,bool> f[N];
int dfs(int u, int p){
si[u] = 1;
for(auto v : g[u]){
if (v == p || vis[v]) continue;
si[u] += dfs(v, u);
}
return si[u];
}
int centroid(int u, int p, int n){
for(auto v : g[u]){
if (v != p && !vis[v] && si[v] > n / 2) return centroid(v, u, n);
}
return u;
}
bool ck(int u, int p, int dep, int up, int down, int k){
if (dep > k) return false;
down = (down * base + s[u]) % mod;
up = (s[u] * pw[dep - 1] + up) % mod;
int val = (up * pw[k - dep] - down + mod) % mod;
if (f[k - dep + 1].find(val) != f[k - dep + 1].end()) return true;
st.pb({dep, val});
mx = max(mx, dep);
for(auto v : g[u]){
if (v != p && !vis[v])
if(ck(v, u, dep + 1, up, down, k)) return true;
}
if (p == curCen){
for(auto x : st){
f[x.fi][x.se] = true;
}
}
return false;
}
bool build(int u, int k){
u = centroid(u, 0, dfs(u, 0));
vis[u] = true;
mx = 0; curCen = u;
f[1][(-s[u] + mod) % mod] = true;
for(auto v : g[u]){
if (vis[v]) continue;
if (ck(v, u, 2, s[u], 0, k)) return true;
}
FOR(i, 0, mx) f[i].clear();
st.clear();
for(auto v : g[u]){
if (!vis[v]){
if (build(v, k)) return true;
}
}
return false;
}
void Proc(){
cin >> n;
FOR(i, 1, n) cin >> s[i];
FOR(i, 1, n - 1){
int u, v;
cin >> u >> v;
g[u].pb(v); g[v].pb(u);
}
pw[0] = 1;
FOR(i, 1, n) pw[i] = pw[i - 1] * base % mod;
int l = 1, r = n / 2, ans = 1;
while (l <= r){
int mid = (l + r) >> 1;
FOR(i, 1, n) vis[i] = false;
if (build(1, 2 * mid + 1)){
ans = max(ans, 2 * mid + 1);
l = mid + 1;
}
else r = mid - 1;
}
l = 1, r = n / 2;
while (l <= r){
int mid = (l + r) >> 1;
FOR(i, 1, n) vis[i] = false;
if (build(1, 2 * mid)){
ans = max(ans, 2 * mid);
l = mid + 1;
}
else r = mid - 1;
}
cout << ans;
}
signed main() {
if(fopen("test.inp", "r")){
freopen("test.inp", "r", stdin);
freopen("test.out", "w", stdout);
}
ios::sync_with_stdio(false);
cin.tie(nullptr);
int T; T = 1;
//cin >> T;
while (T--) Proc();
}
