#include <bits/stdc++.h>
using namespace std;
#define FOR(i, a, b) for(int i = a; i <= b; i++)
#define FOD(i, a, b) for(int i = a; i >= b; i--)
#define fi first
#define se second
#define ll long long
#define db double
#define ii pair<int,int>
#define pb push_back
#define MASK(i) (1LL << i)
#define sq(i) (1LL * (i) * (i))
#define task "khoile08"
#define pow khoile
const ll INF = 1e18;
const int inf = 1e9;
const int N = 5e4 + 2;
const ii mod = {998244353, 1e9 + 7};
const ii base = {311, 311};
ii add(ii a, ii b) {
a.fi += b.fi;
a.se += b.se;
if(a.fi < 0) a.fi += mod.fi;
if(a.se < 0) a.se += mod.se;
if(a.fi >= mod.fi) a.fi -= mod.fi;
if(a.se >= mod.se) a.se -= mod.se;
return a;
}
ii mul(ii a, ii b) {
return {1LL * a.fi * b.fi % mod.fi, 1LL * a.se * b.se % mod.se};
}
int n;
vector<int> g[N];
char c[N];
ii pow[N];
int sze[N];
bool del[N];
map<ii,bool> check[N];
void calsize(int u, int p) {
sze[u] = 1;
for(int v : g[u]) {
if(v == p || del[v]) continue;
calsize(v, u);
sze[u] += sze[v];
}
}
int findcen(int u, int p, int s) {
for(int v : g[u]) {
if(v == p || del[v] || sze[v] <= s / 2) continue;
return findcen(v, u, s);
}
return u;
}
bool cal(int u, int p, ii hu, ii hd, int h, int k, int &maxdepth) {
if(h > k) return false;
maxdepth = max(maxdepth, h);
hu = add(hu, mul({c[u], c[u]}, pow[h - 1]));
if(p != -1) hd = add(mul(hd, base), {c[u], c[u]});
ii tar = add(mul(hu, pow[k - h]), {-hd.fi, -hd.se});
if(check[k - h + 1][tar]) return true;
for(int v : g[u]) {
if(v == p || del[v]) continue;
if(cal(v, u, hu, hd, h + 1, k, maxdepth)) return true;
}
return false;
}
void mark(int u, int p, ii hu, ii hd, int h, int k) {
hu = add(hu, mul({c[u], c[u]}, pow[h - 1]));
if(p != -1) hd = add(mul(hd, base), {c[u], c[u]});
ii tar = add(mul(hu, pow[k - h]), {-hd.fi, -hd.se});
check[h][tar] = 1;
for(int v : g[u]) {
if(v == p || del[v]) continue;
mark(v, u, hu, hd, h + 1, k);
}
}
bool buildcen(int u, int k) {
calsize(u, -1);
int root = findcen(u, -1, sze[u]);
del[root] = 1;
int maxdepth = 1;
ii tmp = {c[root], c[root]};
tmp = mul(tmp, pow[k - 1]);
check[1][tmp] = 1;
for(int v : g[root]) {
if(del[v]) continue;
if(cal(v, root, {c[root], c[root]}, {0, 0}, 2, k, maxdepth)) return true;
mark(v, root, {c[root], c[root]}, {0, 0}, 2, k);
}
FOR(i, 1, maxdepth) check[i].clear();
for(int v : g[root]) {
if(del[v]) continue;
if(buildcen(v, k)) return true;
}
return false;
}
bool can(int k) {
FOR(i, 1, n) {
check[i].clear();
del[i] = 0;
}
return buildcen(1, k);
}
void Solve() {
pow[0] = {1, 1};
FOR(i, 1, n) pow[i] = mul(pow[i - 1], base);
int res = 1;
int l = 1, r = (n + 1) / 2;
while(l <= r) {
int mid = l + r >> 1;
if(can(2 * mid - 1)) {
res = max(res, 2 * mid - 1);
l = mid + 1;
}
else r = mid - 1;
}
l = 1, r = n / 2;
while(l <= r) {
int mid = l + r >> 1;
if(can(2 * mid)) {
res = max(res, 2 * mid);
l = mid + 1;
}
else r = mid - 1;
}
cout << res << '\n';
}
signed main() {
if(fopen(task".inp", "r")) {
freopen(task".inp", "r", stdin);
//freopen(task".out", "w", stdout);
}
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int tc = 1;
// cin >> tc;
while(tc--) {
cin >> n;
FOR(i, 1, n) cin >> c[i];
FOR(i, 1, n - 1) {
int u, v; cin >> u >> v;
g[u].pb(v);
g[v].pb(u);
}
Solve();
}
}
