#include<cstdio>
#include<cstring>
#include<algorithm>
#define MAXN 200000
using namespace std;
typedef long long LL;
struct node
{
	int to;
	node *nxt;
}edges[MAXN*2+5];
node *ncnt=&edges[0],*Adj[MAXN+5];
int n,sum,siz[MAXN+5],mx[MAXN+5],smx[MAXN+5];
int l[MAXN+5],r[MAXN+5];
LL ans=0;
char str[MAXN+5];
void AddEdge(int u,int v)
{
	node *p=++ncnt;
	p->to=v;
	p->nxt=Adj[u];
	Adj[u]=p;
	
	node *q=++ncnt;
	q->to=u;
	q->nxt=Adj[v];
	Adj[v]=q;
}
void DFS1(int u,int fa)
{
	siz[u]=str[u]-'0';
	for(node *p=Adj[u];p!=NULL;p=p->nxt)
	{
		int v=p->to;
		if(v==fa)
			continue;
		DFS1(v,u);
		siz[u]+=siz[v];
		if(mx[v]+1>mx[u])
			smx[u]=mx[u],mx[u]=mx[v]+1;
		else if(mx[v]+1>smx[u])
			smx[u]=mx[v]+1;
	}
}
void DFS2(int u,int fa,int len)
{
	r[u]=len>mx[u]?mx[u]:max(len,smx[u]);
	l[u]=str[u]-'0'?0:(sum-siz[u]?len:MAXN+5);
	if(fa!=-1)
	{
		if(len-1==mx[u])	ans++;
		else if(len-1<mx[u])	ans+=siz[u]<sum;
		else	ans+=siz[u]>0;
	}
	for(node *p=Adj[u];p!=NULL;p=p->nxt)
	{
		int v=p->to;
		if(v==fa)
			continue;
		if(siz[v])
			l[u]=min(l[u],mx[v]+1);
		if(mx[u]==mx[v]+1)
			DFS2(v,u,max(len,smx[u])+1);
		else
			DFS2(v,u,max(len,mx[u])+1);
	}
}
int main()
{
	scanf("%d",&n);
	int u,v;
	for(int i=1;i<n;i++)
	{
		scanf("%d %d",&u,&v);
		AddEdge(u,v);
	}
	scanf("%s",str+1);
	for(int i=1;i<=n;i++)
		sum+=str[i]-'0';
	DFS1(1,-1);
	DFS2(1,-1,0);
	for(int i=1;i<=n;i++)
		if(l[i]<=r[i])
			ans+=r[i]-l[i]+1;
	printf("%lld\n",ans);
	return 0;
}