#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#define PB push_back
#define sz(x) ((int)x.size())
#define all(x) x.begin(),x.end()
using namespace std;
const int N = 50100;
const int PW = 233;
const int PO = 20;
const int md = 998244353;
__gnu_pbds::gp_hash_table<int, bool> mem[N];
vector<int> vc, g[N];
string s;
int ans = 0, kol, siz[N], mem_up[N], mem_down[N], po[N], inv[N], n, hsh[N][2], shsh[N], ANS[N][2];
bool mrk[N];
int mult(int x, int y) { return (1ll * x * y) % md; }
int sum(int x, int y){
x += y;
if (x >= md)
x -= md;
return x;
}
int sub(int x, int y){
x -= y;
if (x < 0)
x += md;
return x;
}
int binpow(int x, int po){
int res = 1;
while (po > 0){
if (po & 1)
res = mult(res, x);
x = mult(x, x);
po >>= 1;
}
return res;
}
void build_sz(int v, int p){
siz[v] = 1;
for (int u : g[v]){
if (u == p || mrk[u]) continue;
build_sz(u, v);
siz[v] += siz[u];
}
}
int search(int v, int p, int SZ){
for (int u : g[v])
if (u != p && !mrk[u] && siz[u] > SZ / 2)
return search(u, v, SZ);
return v;
}
void calc_h(int v, int p, int h1, int h2, int shs, int ht){
hsh[v][0] = h1;
hsh[v][1] = h2;
shsh[v] = shs;
for (int u : g[v]){
if (u == p || mrk[u]) continue;
int ch = s[u] - 'a' + 1;
calc_h(u, v, sum(h1, mult(po[ht], ch)), sum(h2, mult(po[ht + 1], ch)), sum(ch, mult(PW, shs)), ht + 1);
}
}
void change(int v, int p, int ht){
mem[ht][hsh[v][0]] = 1;
for (int u : g[v]){
if (u == p || mrk[u]) continue;
change(u, v, ht + 1);
}
}
void dfs(int v, int p, int ht, int len){
if (ht + 1 > len) return;
int hs = hsh[v][1];
int shs = shsh[v];
mem_up[ht] = shs;
mem_down[ht] = hs;
int c_len = len - (ht + 1);
int c_ht = ht - c_len;
if (c_ht >= 0){
if (mem_up[c_ht] == mem_down[c_ht]) {
int chs = sub(hs, mem_down[c_ht]);
chs = mult(chs, inv[c_ht + 1]);
if (mem[c_len].find(chs) != mem[c_len].end())
kol++;
}
}
for (int u : g[v]){
if (u == p || mrk[u]) continue;
dfs(u, v, ht + 1, len);
}
}
void check(int v, int p, int st){
int l = 0, r = siz[v];
while (l < r){
int md = (l + r + 1) >> 1;
int len = md + md + st;
if (ANS[v][st] >= len){
l = md;
continue;
}
kol = 0;
mem_up[0] = mem_down[0] = s[v] - 'a' + 1;
for (int i = 1; i < siz[v]; i++)
mem[i].clear();
for (int u : g[v]){
if (u == p || mrk[u]) continue;
dfs(u, v, 1, len);
change(u, v, 1);
}
for (int i = 1; i < siz[v]; i++)
mem[i].clear();
for (int it = sz(g[v]) - 1; it >= 0; it--){
int u = g[v][it];
if (u == p || mrk[u]) continue;
dfs(u, v, 1, len);
change(u, v, 1);
}
if (kol > 0)
l = md;
else r = md - 1;
}
ANS[v][st] = max(ANS[v][st], l + l + st);
ans = max(ans, l + l + st);
}
void build_cd(int v, int p){
build_sz(v, p);
v = search(v, p, siz[v]);
build_sz(v, p);
mrk[v] = 1;
for (int u : g[v])
if (u != p && !mrk[u])
build_cd(u, v);
calc_h(v, p, 0, s[v] - 'a' + 1, s[v] - 'a' + 1, 0);
check(v, p, 0);
check(v, p, 1);
if (p >= 0){
ANS[p][0] = max(ANS[v][0], ANS[p][0]);
ANS[p][1] = max(ANS[v][1], ANS[p][1]);
}
mrk[v] = 0;
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
// freopen("217.in","r",stdin);
cin >> n >> s;
po[0] = 1;
for (int i = 1; i <= n; i++) {
po[i] = mult(po[i - 1], PW);
inv[i] = binpow(po[i], md - 2);
}
for (int i = 1; i < n; i++){
int x, y; cin >> x >> y;
x--; y--;
g[x].PB(y);
g[y].PB(x);
}
mem[0][0] = 1;
build_cd(0, -1);
cout << ans;
return 0;
}
