#include<bits/stdc++.h>
using namespace std;
const int N = 1e5+5, mod = 1e9+7, base = 31;
int n, a[N], pw[N], sz[N], CurLen, mxDepth;
bool del[N];
vector<int> adj[N];
map<int,bool> mp[N];
stack<pair<int,int>> save;
bool dfs(int x, int p, int h, int hsh_down, int hsh_up){
if(h+1 > CurLen) return false;
if(!p){
hsh_up = (hsh_up + ((1ll * a[x] * pw[h]) % mod)) % mod;
}
else{
hsh_down = ((1ll * hsh_down * base) % mod + a[x]) % mod;
hsh_up = (hsh_up + ((1ll * a[x] * pw[h]) % mod)) % mod;
}
int check_val = (1ll * hsh_up * pw[CurLen - (h+1)] - 1ll * hsh_down + mod) % mod;
if(!p) mp[h+1][check_val] = true;
if(mp[CurLen - h].count(check_val)) return true;
for(int v : adj[x])if(v != p && !del[v]){
if(dfs(v, x, h+1, hsh_down, hsh_up)) return true;
if(!p){
while(!save.empty()){
pair<int,int> e = save.top();
mp[e.first+1][e.second] = true;
save.pop();
mxDepth = max(mxDepth, e.first+1);
}
}
}
if(p){
save.push(make_pair(h, check_val));
}
return false;
}
int get_Size(int x, int p){
sz[x] = 1;
for(int v : adj[x])if(v != p && !del[v]){
sz[x] += get_Size(v, x);
}
return sz[x];
}
int Centroid(int x, int p, int trsz){
for(int v : adj[x])if(v != p && !del[v] && (sz[v]<<1) > trsz){
return Centroid(v, x, trsz);
}
return x;
}
bool decompose(int x){
x = Centroid(x, -1, get_Size(x, -1));
del[x] = true;
mxDepth = 0;
bool fl = dfs(x, 0, 0, 0, 0);
for(int i = 1; i <= mxDepth; i++) mp[i].clear();
if(fl) return true;
for(int v : adj[x])if(!del[v]){
if(decompose(v)) return true;
}
return false;
}
void solve()
{
cin >> n;
string s; cin >> s;
for(int i = 1; i <= n; i++){
a[i] = s[i-1] - 'a' + 1;
}
for(int i = 1; i < n; i++){
int u,v; cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
pw[0] = 1;
for(int i = 1; i <= n; i++){
pw[i] = (1ll * pw[i-1] * base) % mod;
}
int answer = 0;
int l = 0, r = n/2 + 1;
while(l+1 < r){
int m = l+r>>1;
CurLen = (m<<1);
if(decompose(1)){
l = m;
}
else r = m;
for(int i = 1; i <= n; i++) del[i] = false;
}
answer = max(answer, (l<<1));
l = 0, r = n/2 + 1;
while(l+1 < r){
int m = l+r>>1;
CurLen = (m<<1|1);
if(decompose(1)){
l = m;
}
else r = m;
for(int i = 1; i <= n; i++) del[i] = false;
}
answer = max(answer, (l<<1|1));
cout << answer <<"\n";
return;
}
int32_t main(){
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
#define name "InvMOD"
if(fopen(name".INP", "r")){
freopen(name".INP", "r", stdin);
freopen(name".OUT", "w", stdout);
}
solve();
return 0;
}
