#include<iostream>
#include<cstdio>
using namespace std;

int d1[200005],d2[200005];
int d3[200005],d4[200005];
int n,x,y,siz[200005],col[200005],fa[200005];
long long ans=0;
int tot=0,h[200005];
struct Edge{
	int x,next;
}e[400005];
char ch[200005];

inline void add_edge(int x,int y){
	e[++tot].x=y;
	e[tot].next=h[x],h[x]=tot;
}

void dfs1(int x,int father){
	siz[x]=col[x],fa[x]=father;
	d3[x]=col[x]?0:1e9;
	for(int i=h[x];i;i=e[i].next){
		if(e[i].x==father)continue;
		dfs1(e[i].x,x);
		siz[x]+=siz[e[i].x];
		d1[x]=max(d1[x],d1[e[i].x]+1);
		if(siz[e[i].x])
			d3[x]=min(d3[x],d1[e[i].x]+1);
	}
}

void dfs2(int x,int father){
	if(father)d4[x]=d2[x]-1;
	int maxn=0,sec=0;
	for(int i=h[x];i;i=e[i].next){
		if(e[i].x==father)continue;
		if(d1[e[i].x]+1>maxn)
			sec=maxn,maxn=d1[e[i].x]+1;
		else sec=max(sec,d1[e[i].x]+1);
	}
	for(int i=h[x];i;i=e[i].next){
		if(e[i].x==father)continue;
		if(d1[e[i].x]+1==maxn)
			d2[e[i].x]=max(d2[x],sec)+1;
		else d2[e[i].x]=max(d2[x],maxn)+1;
		dfs2(e[i].x,x);
	}
}

int main(){
	scanf("%d",&n);
	for(int i=1;i<n;i++){
		scanf("%d%d",&x,&y);
		add_edge(x,y);
		add_edge(y,x);
	}
	scanf("%s",ch+1);
	for(int i=1;ch[i];i++)
		col[i]=ch[i]-'0';
	dfs1(1,0),dfs2(1,0);
	for(int i=1;i<=n;i++){
		int minv,maxv;
		minv=min(d3[i],siz[1]==siz[i]?(int)1e9:d2[i]);
		maxv=max(d1[i],d2[i])-1;
		for(int j=h[i];j;j=e[j].next){
			if(e[j].x==fa[i])maxv=min(maxv,d1[i]+1);
			else maxv=min(maxv,d4[e[j].x]+1);
		}
		if(maxv>=minv)ans+=1LL*maxv-minv+1;
	}
	printf("%lld",ans+1);
}