// iee
#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <vector>
#include <set>
#include <map>
#define rep(i, a, b) for (auto i = (a); i <= (b); ++i)
#define per(i, a, b) for (auto i = (a); i >= (b); --i)
#define fi first
#define se second
using ll = long long;
using ull = unsigned long long;
using namespace std;
void work(int);
template <class T> void read(T &x) {
x = 0; int f = 1, ch = getchar();
while (!isdigit(ch)) { if (ch == '-') f = -1; ch = getchar(); }
while (isdigit(ch)) x = x * 10 + (ch - '0'), ch = getchar();
x *= f;
}
int main() {
int TT = 1; // cin >> TT;
rep(CAS, 1, TT)
work(CAS);
return 0;
}
const int N = 5e4 + 5;
int n, u[N], v[N];
char a[N];
namespace bf {
const int N = 3005, base = 31;
vector<int> e[N];
ull hpath[N][N];
void dfs1(const int &rt, int u, int pr, ull h) {
h = h * base + (a[u] - 'a' + 1);
hpath[rt][u] = h;
for (int v: e[u]) if (v != pr)
dfs1(rt, v, u, h);
}
int ans, st[N], top;
void dfs2(const int &rt, int u, int pr) {
st[++top] = u;
if (top % 2 == 0 && hpath[rt][st[top / 2]] == hpath[u][st[top / 2 + 1]] || top % 2 == 1 && hpath[rt][st[top / 2 + 1]] == hpath[u][st[top / 2 + 1]]) ans = max(ans, top);
for (int v: e[u]) if (v != pr)
dfs2(rt, v, u);
--top;
}
void work() {
rep(i, 1, n - 1) e[::u[i]].push_back(::v[i]), e[::v[i]].push_back(::u[i]);
rep(i, 1, n) dfs1(i, i, -1, 0ull);
rep(i, 1, n) top = 0, dfs2(i, i, 0);
cout << ans;
}
}
namespace lian {
vector<int> e[N];
const int base = 31;
char s[N];
int tot;
void dfs(int u, int pr) {
s[++tot] = a[u];
for (int v: e[u]) if (v != pr)
dfs(v, u);
}
ull h[N], hr[N], pw[N];
ull qh(int l, int r) { return h[r] - h[l - 1] * pw[r - l + 1]; }
ull qhr(int l, int r) { return hr[l] - hr[r + 1] * pw[r - l + 1]; }
void work() {
rep(i, 1, n - 1) e[::u[i]].push_back(v[i]), e[::v[i]].push_back(::u[i]);
rep(i, 1, n) if (e[i].size() == 1) { dfs(i, 0); break; }
rep(i, 1, n) h[i] = h[i - 1] * base + (s[i] - 'a' + 1);
per(i, n, 1) hr[i] = hr[i + 1] * base + (s[i] - 'a' + 1);
pw[0] = 1;
rep(i, 1, n) pw[i] = pw[i - 1] * base;
int ans = 0;
rep(i, 1, n) {
int l = 1, r = min(i, n - i + 1);
while (l < r) {
int mid = l + r + 1 >> 1;
if (qh(i - mid + 1, i) == qhr(i + 1, i + mid)) l = mid;
else r = mid - 1;
}
ans = max(ans, l * 2);
l = 1, r = min(i, n - i + 1);
while (l < r) {
int mid = l + r + 1 >> 1;
if (qh(i - mid + 1, i) == qhr(i, i + mid - 1)) l = mid;
else r = mid - 1;
}
ans = max(ans, l * 2 - 1);
}
cout << ans;
}
}
void work(int CASE) {
scanf("%d%s", &n, a + 1);
rep(i, 1, n - 1) scanf("%d%d", u + i, v + i);
if (n <= 3000) { bf::work(); return; }
lian::work();
}
