#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> ii;
string act;
vector<int> adj[50010];
set<string> bigmap,smallmap;
set<string> m1,m2;
void dfs(int u,int pa,string s){
smallmap.insert(s);
//cout << s << "hi\n";
//cout << s << "hi\n";
for (int v: adj[u]){
if (v == pa) continue;
dfs(v,u,s+act[v]);
}
}
void dfs1(int u,int pa,string s){
m1.insert(s);
//cout << s << "hi\n";
//cout << s << "hi\n";
for (int v: adj[u]){
if (v == pa) continue;
dfs1(v,u,s+act[v]);
}
}
void dfs2(int u,int pa,string s){
m2.insert(s);
//cout << s << "hi\n";
//cout << s << "hi\n";
for (int v: adj[u]){
if (v == pa) continue;
dfs2(v,u,s+act[v]);
}
}
int main(){
int n;
cin >> n;
cin >> act;
//cout << act << "read\n";
ii edge[n-1];
for (int i = 0; i < n-1; i++){
int a,b;
cin >> a >> b;
a--;
b--;
adj[a].push_back(b);
adj[b].push_back(a);
edge[i] = ii(a,b);
}
int ans = 0;
for (int i = 0; i < n; i++){
bigmap.clear();
for (int j = 0; j < adj[i].size(); j++) {
smallmap.clear();
string s = "";
s += act[adj[i][j]];
dfs(adj[i][j],i,s);
for (auto it = smallmap.begin(); it != smallmap.end(); ++it){
if (bigmap.find(*it) != bigmap.end()) ans = max(ans,2*(int)((*it).length())+1);
else bigmap.insert(*it);
}
}
// cout << "hi\n";
}
for (int i = 0; i < n-1; i++){
int a = edge[i].first,b = edge[i].second;
string s1 = "",s2 = "";
s1 += act[a],s2+= act[b];
m1.clear();
m2.clear();
dfs1(a,b,s1);
dfs2(b,a,s2);
for (auto it = m1.begin(); it != m1.end(); ++it){
//cout<< it->first << " " << it->second << "\n";
if (m2.find(*it) != m2.end()) ans = max(ans,2*(int)((*it).length()));
}
}
cout << ans;
}
