#include <bits/stdc++.h>
using namespace std;
#define int long long
#define TASK "NOEL"
#define REP(i, n) for(int i = 1; i <= n; i++)
#define FOR(i, a, b) for(auto i = a; i <= b; i++)
#define FORD(i, a, b) for(auto i = a; i >= b; i--)
template<class T> bool maximize(T& a, T b) { if(a < b) return a = b, 1; return 0; }
template<class T> bool minimize(T& a, T b) { if(a > b) return a = b, 1; return 0; }
mt19937 rng(time(0));
const int N = (int)3e3 + 7, Base = 127, MOD = (int)1e9 + 7, MM = MOD * MOD;
const int N2 = (int)5e4 + 7;
int n;
vector<int> adj[N2];
int c[N2], path[N][N], len[N][N], pref[N2], suf[N2], po[N2];
void Read()
{
cin >> n;
REP(i, n)
{
char x;
cin >> x;
c[i] = x;
}
REP(i, n - 1)
{
int u, v;
cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
}
}
int cur;
void DFS(int u, int p = -1)
{
for(int v : adj[u])
{
if(v == p)
continue;
path[cur][v] = (1ll * path[cur][u] * Base + c[v]) % MOD;
len[cur][v] = len[cur][u] + 1;
DFS(v, u);
}
}
int GetPref(int l, int r)
{
return (pref[r] - pref[l - 1] * po[r - l + 1] + MM) % MOD;
}
int GetSuf(int l, int r)
{
return (suf[l] - suf[r + 1] * po[r - l + 1] + MM) % MOD;
}
void Subtask2()
{
REP(i, n) pref[i] = (pref[i - 1] * Base + c[i]) % MOD;
FORD(i, n, 1) suf[i] = (suf[i + 1] * Base + c[i]) % MOD;
po[0] = 1;
REP(i, n) po[i] = po[i - 1] * Base % MOD;
int l = 0, r = n + 1;
int ans = 1;
while(r - l > 1)
{
int m = l + r >> 1;
bool ok = 0;
REP(i, n)
{
if(i + m > n || i - m < 1) continue;
if(GetPref(i + 1, i + m) == GetSuf(i - m, i - 1))
{
ok = 1;
break;
}
}
if(ok) l = m;
else r = m;
}
ans = l << 1 | 1;
l = -1, r = n + 1;
while(r - l > 1)
{
int m = l + r >> 1;
bool ok = 0;
REP(i, n)
{
if(i + m - 1 > n || i - m < 1) continue;
if(GetPref(i, i + m - 1) == GetSuf(i - m, i - 1))
{
ok = 1;
break;
}
}
if(ok) l = m;
else r = m;
}
maximize(ans, l << 1);
cout << ans << endl;
}
void Solve()
{
if(n > 3000) return Subtask2();
REP(i, n)
{
cur = i;
path[cur][cur] = c[cur];
DFS(i);
}
int ans = 0;
REP(i, n)
REP(j, n)
{
if(path[i][j] == path[j][i])
maximize(ans, len[i][j] + 1);
}
cout << ans << endl;
}
signed main(void)
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
if(fopen("TASK.INP", "r")) freopen("TASK.INP", "r", stdin);
if(fopen(TASK".INP", "r"))
{
freopen(TASK".INP", "r", stdin);
freopen(TASK".OUT", "w", stdout);
}
Read();
Solve();
return 0;
}
/*
7
iannade
1 2
2 3
3 4
4 5
5 6
6 7
*/
