#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define eb emplace_back
#define pb push_back
#define fi first
#define se second
#define ii pair<int,int>
#define ve vector
#define all(x) x.begin(), x.end()
#define fo(i,a,b) for (int i=(a); i<=(b); ++i)
#define fd(i,a,b) for (int i=(a); i>=(b); --i)
#define maxi(a, b) a = max(a, b)
#define mini(a, b) a = min(a, b)
#define siz(x) ((int)(x).size())
#define vi ve<int>
#define _ << ' ' <<
const int N = 50500, inf = 1e9+10, mod1 = 1e9+7, base = 11111;
/**
**/
bool MBE;
int bpw(int a, int b) {
int res = 1;
for (; b; b>>=1, a=1LL*a*a%mod1)
if (b&1) res=1LL*res*a%mod1;
return res;
}
struct H {
int val;
H(){val=0;}
H(int x){val=x;if(val>=mod1)val-=mod1;}
H operator+(H x) {return H(val+x.val);}
H operator*(H x) {return H(1LL*val*x.val%mod1);}
H operator-(H x) {return H(val-x.val+mod1);}
H operator/(H x) {return H(1LL*val*bpw(x.val, mod1-2)%mod1);}
bool operator==(H x) {return val==x.val;}
int toInt() {return val;}
};
int n, a[N], len, sz[N], maxH;
vi g[N]; bool del[N], pal[N];
H down[N], up[N], pw[N];
unordered_set<int> f[N];
void dfs(int u, int p = -1) {
sz[u] = 1;
for (int v : g[u]) if (v!=p&&!del[v]) {
dfs(v, u);
sz[u] += sz[v];
}
}
int findcen(int u, int p, int tot) {
for (int v : g[u]) if (v!=p&&!del[v]&&sz[v]*2>tot)
return findcen(v, u, tot);
return u;
}
int stk[N], Head;
bool find(int u, int p, int h, H hu, H hd) {
maxi(maxH, h);
if (h > len) return 0;
stk[++Head] = u;
hd = hd * base + a[u];
hu = hu + pw[h-1] * a[u];
down[u] = hd, up[u] = hu;
pal[u] = (hu == hd);
if (pal[u] && h == len) return 1;
if (h * 2 >= len) {
int need = len - h;
int x = stk[Head - need];
if (pal[x]) {
H cur = (hd - down[x] * pw[need]);
if (f[need].count(cur.toInt()))
return 1;
}
}
for (int v:g[u]) if (v!=p&&!del[v])
if (find(v, u, h+1, hu, hd))
return 1;
Head--;
return 0;
}
void ins(int u, int p, int h, H hu, H hd) {
maxi(maxH, h);
hd = hd * base + a[u];
f[h].insert(hd.toInt());
for (int v:g[u]) if (v!=p&&!del[v])
ins(v, u, h+1, hu, hd);
}
bool go(int u) {
if (len == 1) return 1;
dfs(u);
int cen = findcen(u, -1, sz[u]);
del[cen] = 1;
maxH = Head = 0;
down[cen] = up[cen] = H(a[cen]); pal[cen]=1;
stk[++Head] = cen;
for (int v:g[cen]) if (!del[v]) {
if (find(v, cen, 2, H(a[cen]), H(a[cen]))) {
return 1;
}
ins(v, cen, 1, H(0), H(0));
}
Head = 0;
fo(i,0,maxH) f[i].clear();
reverse(all(g[cen]));
stk[++Head] = cen;
for (int v:g[cen]) if (!del[v]) {
if (find(v, cen, 2, H(a[cen]), H(a[cen]))) {
return 1;
}
ins(v, cen, 1, H(0), H(0));
}
Head = 0;
fo(i,0,maxH) f[i].clear();
for (int v:g[cen]) if (!del[v]&&go(v)) return 1;
return 0;
}
bool check(int x) {
fo(i,1,n) f[i].clear(), del[i]=0, pal[i]=0;
len = x;
return go(1);
}
void sol() {
cin >> n;
pw[0]=1;
fo(i,1,n) pw[i]=pw[i-1]*base;
fo(i,1,n) {
char c; cin >> c;
a[i] = c-'a'+1;
}
fo(i,1,n-1) {
int u, v; cin >> u >> v;
g[u].pb(v), g[v].pb(u);
}
int l = 0, r = n / 2, mid, res = 0;
while (l <= r) {
mid = (l + r) / 2;
if (mid==0||check(2*mid)) {
maxi(res, 2*mid);
l = mid + 1;
} else {
r = mid - 1;
}
}
l = 0, r = n / 2, mid;
while (l <= r) {
mid = (l + r) / 2;
if (check(2 * mid + 1)) {
maxi(res, 2*mid+1);
l = mid + 1;
} else {
r = mid - 1;
}
}
cout << res;
}
bool MED;
signed main(){
ios::sync_with_stdio(0); cin.tie(0);
if(fopen("A.inp","r")) {
freopen("A.inp","r",stdin);
freopen("A.out","w",stdout);
}
int tc = 1; // cin >> tc;
fo(i,1,tc) sol();
// cerr << "Memory = " << abs(&MED - &MBE)/1024.0/1024.0 << " MB";
return 0;
}
