#pragma GCC optimize("O3,unroll-loops")
#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
#define fi first
#define se second
#define ll long long
#define pb push_back
#define db(val) "[" #val " = " << (val) << "] "
const ll mod = 1e9 + 7;
const int maxn = 1e5 + 4;
const int INF = 1e9;
const ll base = 31;
const int N = 16;
int n, len, root, used[maxn], h[maxn];
string s;
vector<int> adj[maxn], nodes;
ll Pow[maxn], up[maxn], down[maxn];
gp_hash_table<ll,int> L;
bool flag;
ll add(ll a, ll b) {
a += b;
return a;
}
ll del(ll a, ll b) {
a -= b;
return a;
}
void pre(int u, int p) {
if (p)
down[u] = add(down[p], (s[u] - 'a' + 1) * Pow[h[u] - 1]);
if (p)
up[u] = add(up[p] * base, s[u] - 'a' + 1);
L[up[u]]++;
for (int v : adj[u])
if (v != p && !used[v]) {
h[v] = h[u] + 1;
pre(v, u);
}
}
void dfs(int u, int p) {
if (len < h[u] || flag) return;
nodes.pb(u);
int k = len - h[u] - 1, c = 0;
if (int(nodes.size()) > h[u] - k && h[u] - k >= 0)
c = nodes[h[u] - k];
if (c && add(up[c], (s[root] - 'a' + 1) * Pow[h[c]]) ==
add(down[c] * base, (s[root] - 'a' + 1))) {
if (k == 0)
return flag = true, void();
ll val = del(up[u], up[c] * Pow[k]) ;
if (L.find(val) != L.end()) {
return flag = true, void();
}
}
for (int v : adj[u])
if (v != p && !used[v])
dfs(v, u);
nodes.pop_back();
}
void reset(int u, int p, int val) {
L[up[u]] += val;
if (L[up[u]] == 0)
L.erase(up[u]);
for (int v : adj[u])
if (v != p && !used[v])
reset(v, u, val);
}
void Solve(int c) {
h[c] = 0;
up[c] = down[c] = 0;
L.clear();
pre(c, 0);
nodes.clear();
nodes.pb(c);
for (int v : adj[c])
if (!used[v]) {
if (flag) return;
reset(v, c, -1);
dfs(v, c);
reset(v, c, 1);
}
nodes.pop_back();
}
struct Centroid_Decomposition {
int sz[maxn];
int dfs(int u, int p) {
sz[u] = 1;
for (int v : adj[u])
if (!used[v] && v != p)
sz[u] += dfs(v, u);
return sz[u];
}
int Centroid(int u, int p, int tot) {
for (int v : adj[u])
if (!used[v] && v != p && sz[v] > tot / 2)
return Centroid(v, u, tot);
return u;
}
void build(int u) {
if (flag) return;
int c = Centroid(u, 0, dfs(u, 0));
root = c;
Solve(c);
used[c] = 1;
for (int v : adj[c])
if (!used[v])
build(v);
}
} Cen;
bool ok(int m, int sign) {
flag = false;
len = 2 * m + sign;
memset(used, 0, sizeof used);
Cen.build(1);
return flag;
}
int main()
{
ios::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
//freopen(".INP", "r", stdin);
//freopen(".OUT", "w", stdout);
cin >> n >> s;
s = ' ' + s;
for (int i = 1; i < n; i++) {
int u, v; cin >> u >> v;
adj[u].pb(v);
adj[v].pb(u);
}
Pow[0] = 1;
for (int i = 1; i <= n; i++) {
Pow[i] = Pow[i - 1] * base;
}
// return cout << ok(2, 1), 0;
int L = 1, R = n / 2, res = 1;
while (L <= R) {
int mid = (L + R) / 2;
if (ok(mid, 1)) {
res = 2 * mid + 1;
L = mid + 1;
}
else R = mid - 1;
}
L = 1, R = n / 2;
while (L <= R) {
int mid = (L + R) / 2;
if (ok(mid, 0)) {
res = max(res, 2 * mid);
L = mid + 1;
}
else R = mid - 1;
}
cout << res;
}
