#include <bits/stdc++.h>
#define d 256
#define MOD 1000000007
using namespace std;
/*
Avem un arbore cu n noduri, fiecare nod initial are o culoare.
Numim segment palindromic [u, v] daca lantul parcus de la u->v e acelasi cu cel parcus de la v->u
Trebuie sa gasim cel mai lung segment palindromic.
*/
const int NMAX(50005);
using ll = long long;
ll putH[NMAX], h[NMAX];
int cul[NMAX], dist[NMAX], dp[NMAX][18], dad[NMAX];
vector<int> G[NMAX];
bool viz[NMAX];
inline void precalc(int nod)
{
for(int pt = 1; pt <= 17; ++pt)
if(dp[nod][pt - 1] != -1)
dp[nod][pt] = dp[dp[nod][pt - 1]][pt - 1];
viz[nod] = 1;
for(auto it: G[nod])
if(!viz[it])
{
dad[it] = nod;
dp[it][0] = nod;
h[it] = (h[nod] * d + cul[it]) % MOD;
dist[it] = dist[nod] + 1;
precalc(it);
}
}
inline int LCA(int x, int y)
{
if(dist[x] < dist[y])
swap(x, y);
for(int pt = 17; pt >= 0; --pt)
if(dist[x] - (1 << pt) >= dist[y])
x = dp[x][pt];
if(x == y)
return x;
for(int pt = 17; pt >= 0; -- pt)
if(dp[x][pt] != -1 && dp[y][pt] != -1 && dp[x][pt] != dp[y][pt])
x = dp[x][pt], y = dp[y][pt];
return dp[x][0];
}
inline int getD(int x, int dist)
{
for(int pt = 17; pt >= 0; --pt)
if(dist - (1 << pt) >= 0)
x = dp[x][pt], dist -= (1 << pt);
return x;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0), cout.tie(0);
int n;
string s;
cin >> n >> s;
for(int i = 0; i < n; ++i)
cul[i + 1] = s[i];
for(int i = 1; i < n; ++i)
{
int x, y;
cin >> x >> y;
G[x].push_back(y);
G[y].push_back(x);
}
for(int i = 1; i <= n; ++i)
for(int pt = 0; pt <= 17; ++pt)
dp[i][pt] = -1;
dp[1][0] = 0;
h[1] = cul[1];
precalc(1);
putH[0] = 1;
for(int p = 1; p <= n; ++p)
putH[p] = putH[p] * d % MOD;
int maxx = 0;
for(int nodS = 1; nodS <= n; ++nodS)
for(int nodD = nodS + 1; nodD <= n; ++nodD)
{
int lc = LCA(nodS, nodD);
if(nodS != lc && nodD != lc)
{
int st = nodS, dr = nodD;
if(dist[st] > dist[dr])
swap(st, dr);
ll h1 = (h[st] - h[dad[lc]] * putH[dist[dad[lc]]] % MOD + MOD) % MOD;
int care = getD(dr, dist[st] - dist[lc] + 1);
ll h2 = (h[dr] - h[care] * putH[dist[care]] % MOD + MOD) % MOD;
//cerr << h1 << ' ' << h2 << '\n';
if(h1 == h2)
{
int i = getD(nodD, dist[nodD] - dist[lc] - 1);
int j = dad[care];
bool ok = 1;
while(dist[i] < dist[j])
{
if(cul[i] != cul[j])
{
ok = 0;
break;
}
++i, --j;
}
if(ok)
maxx = max(maxx, dist[nodS] - dist[lc] + dist[nodD] - dist[lc] + 1);
}
}
else
{
int st = nodS, dr = nodD;
if(dist[st] > dist[dr])
swap(st, dr);
bool ok = 1;
while(dist[st] < dist[dr])
{
if(cul[st] != cul[dr])
{
ok = 0;
break;
}
++st, --dr;
}
if(ok)
maxx = max(maxx, abs(dist[nodD] - dist[nodS]) + 1);
}
}
cout << maxx << '\n';
return 0;
}
