#include<bits/stdc++.h>
#define ll long long
#define int long long
#define fr(i,j,k) for(register int i=j;i<=k;++i)
#define rf(i,j,k) for(register int i=j;i>=k;--i)
#define foredge(i,j) for(register int i=head[j];i;i=e[i].nxt)
#define pb push_back
#define Times printf("Time:%.3lf\n",clock()/CLOCKS_PER_SEC)
#define pii pair<int,int>
#define mk make_pair
using namespace std;
inline int read(){
	int x=0;
	bool f=0;
	char c=getchar();
	while(!isdigit(c)) f|=(c=='-'),c=getchar();
	while(isdigit(c)) x=(x<<3)+(x<<1)+(c^48),c=getchar();
	return f?-x:x;
}
inline void write(int x){
    if(x<0){putchar('-');x=-x;}
    if(x>9)write(x/10);
    putchar(x%10+'0');
}
inline void writeln(int x){write(x); puts("");}
inline void writepl(int x){write(x); putchar(' ');}
mt19937 rnd(chrono::steady_clock::now().time_since_epoch().count());
inline int randfind(int l,int r){return rnd()%(r-l+1)+l;}
//inline void init(){
//	int t=read();
//	while(t--) work();
//}
const int Maxn=3e5+10;
ll f[Maxn][2][2];
vector<int> vc[Maxn];
int n;
char c[Maxn];
int ln;
inline void init(){
    n=read();scanf("%s",c+1);ln=strlen(c+1);
    fr(i,1,n-1){
        int x,y;
        x=read();y=read();
        vc[x].pb(y);vc[y].pb(x);
    }
}
int d[Maxn];
int flag;
inline bool cmp(ll a,ll b){return a>b;}
inline void chkmin(ll &x,ll y){if(x>y) x=y;}
inline void chkmax(ll &x,ll y){if(x<y) x=y;}
inline void dfs(int x,int fa){
    for(auto y:vc[x]) if(y!=fa) dfs(y,x);
    fr(nowtp,0,1){
        vector<ll> now;vector<ll> ().swap(now);
        ll s=0;
        for(auto y:vc[x]) if(y!=fa) now.pb(f[y][1][nowtp]-f[y][0][nowtp]),s=f[y][0][nowtp];
        sort(now.begin(),now.end());reverse(now.begin(),now.end());now.pb(0);
        fr(fatp,0,1-(!fa)){
            ll nows=s;
            for(int j=0;j<now.size();++j){
                int id=fatp+j,add=0;
                if(flag==1) add=1ll*id*(id-1);
                if(flag==2) add=1ll*id*(d[x]-id);
                if(flag==3) add=1ll*(id/2)*((id+1)/2);
                // cout<<nows<<' '<<nowtp<<endl;
                chkmax(f[x][nowtp][fatp],nows+add*(nowtp==0));
                nows+=now[j];
            }
        }
    }
}
inline void work(){
    fr(i,1,n) d[i]=vc[i].size();
    if(ln==1){
        writeln(n);
        return;
    }
    if(ln==2){
        if(c[1]==c[2]) writeln(2*(n-1));
        else writeln(n-1);
        return;
    }
    if(c[1]==c[2] && c[2]==c[3]){
        ll ans=0;
        fr(i,1,n) ans+=1ll*d[i]*(d[i]-1);
        printf("%lld\n",ans);
        return;
    }
    if(c[1]==c[3]) flag=1;
    else if(c[1]==c[2]) flag=2;
    else if(c[2]==c[3]) flag=2;
    else flag=3;
    dfs(1,0);
    printf("%lld\n",max(f[1][0][0],f[1][1][0]));
}
signed main(){
	// freopen("input.in","r",stdin);
	// freopen("output.out","w",stdout);
    init();work();
    // printf("\nTIME:%.3lf",(double)clock()/CLOCKS_PER_SEC);
	return 0;
}