#include <bits/stdc++.h>
#define ll long long
#define LOG 20
#define MASK(i) (1LL<<(i))
#define BIT(x,i) (((x)>>(i))&1)
#define FIRST_BIT(mask) __builtin_ctz((mask)&(-mask))
#define ERASE_BIT(mask) (mask)^((mask)&(-mask))
#define left _left
#define right _right
#define task "t"
using namespace std;
const ll INF=1e18;
const int iat=1e5+9;
const int mod=1e9+7;
const int base=31;
void fast_IO()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
cout.tie(0);
if(fopen(task".inp","r"))
{
freopen(task".inp","r",stdin);
freopen(task".out","w",stdout);
}
}
int n;
char s[iat];
vector <int> g[iat],node;
int child[iat],dep[iat],f[iat][LOG];
bool visited[iat],res;
ll pw[iat],HashUp[iat],HashDown[iat];
vector <pair<ll,int>> store[iat];
void dfs(int u, int par)
{
child[u]=1;
for(auto v : g[u])
{
if(v!=par && !visited[v])dfs(v,u),child[u]+=child[v];
}
}
int centroid(int u, int par, int sz)
{
for(auto v : g[u])
{
if(v!=par && !visited[v])
{
if(child[v]>sz/2)return centroid(v,u,sz);
}
}
return u;
}
void calc(int u, int par)
{
node.push_back(u);
store[dep[u]].push_back(make_pair(HashDown[u],u));
for(int i=1; MASK(i)<=n; i++)f[u][i]=f[f[u][i-1]][i-1];
for(int v : g[u])
{
if(v!=par && !visited[v])
{
f[v][0]=u;
dep[v]=dep[u]+1;
HashDown[v]=HashDown[u]*base+s[v]-'a'+1;
HashUp[v]=HashUp[u]+pw[dep[v]-1]*(s[v]-'a'+1);
calc(v,u);
}
}
}
int lift(int x, int k)
{
for(int i=LOG-1; i>=0; i--)
{
if(BIT(k,i))x=f[x][i];
}
return x;
}
int LCA(int u, int v)
{
if(u==v)return u;
if(dep[u]<dep[v])swap(u,v);
int k=dep[u]-dep[v];
for(int i=LOG-1; i>=0; i--)
{
if(BIT(k,i))u=f[u][i];
}
if(u==v)return u;
for(int i=LOG-1; i>=0; i--)
{
if(f[u][i]!=f[v][i])u=f[u][i],v=f[v][i];
}
return f[u][0];
}
ll GetHash(int u, int v)
{
return HashDown[u]-HashDown[f[v][0]]*pw[dep[u]-dep[v]+1];
}
void solve(int u, int len)
{
if(res)return;
HashUp[u]=s[u]-'a'+1;
HashDown[u]=s[u]-'a'+1;
node.clear();
f[u][0]=0,dep[u]=1;
calc(u,u);
for(int i=1; i<=n; i++)
{
if(store[i].empty())break;
sort(store[i].begin(),store[i].end());
}
for(int it : node)
{
if(res)break;
int dneed=len-dep[it]+1;
if(dneed>dep[it] || dneed<1)continue;
int X=lift(it,dneed-1);
if(HashDown[X]!=HashUp[X])continue;
ll tmp=GetHash(it,X);
int l=lower_bound(store[dneed].begin(),store[dneed].end(),make_pair(tmp,-1))-store[dneed].begin();
if(l==store[dneed].size() || store[dneed][l].first!=tmp)continue;
while(l<store[dneed].size())
{
if(store[dneed][l].first!=tmp)break;
if(LCA(it,store[dneed][l].second)==u)
{
res=true;
break;
}
l++;
}
}
for(int i=1; i<=n; i++)
{
if(store[i].empty())break;
store[i].clear();
}
}
void build_tree(int u, int len)
{
if(res)return;
dfs(u,u);
int x=centroid(u,u,child[u]);
visited[x]=true;
solve(x,len);
for(int v : g[x])
{
if(!visited[v])build_tree(v,len);
}
}
bool check(int x)
{
for(int i=1; i<=n; i++)visited[i]=false;
res=false;
build_tree(1,x);
return res;
}
signed main()
{
fast_IO();
cin>>n;
pw[0]=1;
for(int i=1; i<=n; i++)pw[i]=pw[i-1]*base;
for(int i=1; i<=n; i++)cin>>s[i];
for(int i=1; i<n; i++)
{
int a,b;
cin>>a>>b;
g[a].push_back(b);
g[b].push_back(a);
}
int ans=1;
int l=1,r=n/2;
while(l<=r)
{
int mid=(l+r)/2;
int val=mid*2+1;
if(check(val))ans=max(ans,val),l=mid+1;
else r=mid-1;
}
l=1,r=n/2;
while(l<=r)
{
int mid=(l+r)/2;
int val=mid*2;
if(check(val))ans=max(ans,val),l=mid+1;
else r=mid-1;
}
cout<<ans;
}
