#include<bits/stdc++.h>
#define MASK(i) (1 << (i))
#define pub push_back
#define all(v) v.begin(), v.end()
#define compact(v) v.erase(unique(all(v)), end(v))
#define pii pair<int,int>
#define fi first
#define se second
#define endl "\n"
#define sz(v) (int)(v).size()
using namespace std;
template<class T> bool minimize(T& a, T b){if(a > b) return a = b, true;return false;}
template<class T> bool maximize(T& a, T b){if(a < b) return a = b, true;return false;}
typedef long long ll;
typedef long double ld;
mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rand_range(ll l, ll r){return uniform_int_distribution<ll>(l, r)(rng);}
const int N = 1e5 + 15;
const int MOD = 1e9 + 7;
const int base = 311;
int add(int a, int b) {if(a >= MOD - b) return a - MOD + b; return a + b;}
int sub(int a, int b) {if(a < b) return a + MOD - b; return a - b;}
int mul(int a, int b) {return 1LL*a*b % MOD;}
int n;
char a[N];
vector<int> g[N];
int pw[N];
int sz[N];
bool is_centroid[N];
int dfs_sz(int u, int p){
sz[u] = 1;
for(int v : g[u]) if(v != p){
if(is_centroid[v]) continue;
sz[u] += dfs_sz(v,u);
}
return sz[u];
}
int find_centroid(int u, int p, int tree_sz){
for(int v : g[u]) if(v != p){
if(!is_centroid[v] && 2*sz[v] > tree_sz) return find_centroid(v,u,tree_sz);
}
return u;
}
deque<pii> save;
int mx_h;
map<int,bool> mp[N];
bool make_dist(int u, int p, int cur_dist, int hash_up, int hash_down,int cur_len){
if(cur_dist > cur_len) return 0;
maximize(mx_h, cur_dist);
if(p != -1) hash_down = add(mul(hash_down,base), a[u] - 'a' + 1);
hash_up = add(hash_up, mul(pw[cur_dist-1], a[u] - 'a' + 1));
int x = sub(mul(hash_up, pw[cur_len-cur_dist]), hash_down);
if(p == -1) mp[cur_dist][x] = 1;
else if(mp[cur_len-cur_dist+1].count(x)) return true;
save.pub({cur_dist,x});
bool ok = false;
for(int v : g[u]) if(v != p){
if(is_centroid[v]) continue;
ok |= make_dist(v,u,cur_dist+1,hash_up,hash_down,cur_len);
if(ok) return true;
if(p == -1){
while(!save.empty()){
mp[save.back().fi][save.back().se] = 1;
save.pop_back();
}
}
}
return ok;
}
bool build_centroid(int u, int cur_len){
u = find_centroid(u,-1,dfs_sz(u,-1));
is_centroid[u] = true;
mx_h = 0;
bool ok = make_dist(u,-1,1,0,0,cur_len);
for(int i = 0; i <= mx_h; i++) mp[i].clear();
while(!save.empty()) save.pop_back();
if(ok) return true;
for(int v : g[u]) if(!is_centroid[v]){
ok |= build_centroid(v,cur_len);
if(ok) return true;
}
return ok;
}
bool check(int cur_len){
bool ok = build_centroid(1,cur_len);
for(int i = 1; i <= n; i++) is_centroid[i] = false;
return ok;
}
void solve(){
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;
g[u].pub(v);
g[v].pub(u);
}
pw[0] = 1;
for(int i = 1; i <= n; i++) pw[i] = mul(pw[i-1], base);
int ans = 1;
int l = 1, r = n/2;
while(l <= r){
int mid = (l+r) >> 1;
if(check(mid<<1)){
ans = max(ans, mid << 1);
l = mid+1;
}
else r = mid - 1;
}
l = 1, r = n/2;
while(l <= r){
int mid = (l+r) >> 1;
if(check(mid<<1|1)){
ans = max(ans, mid << 1|1);
l = mid + 1;
}
else r = mid-1;
}
cout << ans;
}
signed main(){
ios_base::sync_with_stdio(NULL);
cin.tie(0); cout.tie(0);
#define task "task"
if(fopen(task".INP", "r")){
freopen(task".INP", "r", stdin);
freopen(task".OUT", "w", stdout);
}
int t; t = 1; //cin >> t;
while(t--) solve();
}
