#include<bits/stdc++.h>
typedef long long ll;
ll gi(){
	ll x=0,f=1;
	char ch=getchar();
	while(!isdigit(ch))f^=ch=='-',ch=getchar();
	while(isdigit(ch))x=x*10+ch-'0',ch=getchar();
	return f?x:-x;
}
char S[200010];
int fir[200010],dis[400010],nxt[400010],id;
void link(int a,int b){nxt[++id]=fir[a],fir[a]=id,dis[id]=b;}
int F[200010],cF[200010],sz[200010];
void dfs(int x,int fa=-1){
	sz[x]=S[x]-'0';
	for(int i=fir[x];i;i=nxt[i]){
		if(fa==dis[i])continue;
		dfs(dis[i],x);
		if(F[dis[i]]>=F[x])cF[x]=F[x],F[x]=F[dis[i]]+1;
		else cF[x]=std::max(cF[x],F[dis[i]]+1);
		sz[x]+=sz[dis[i]];
	}
}
ll ans;
void DFS(int x,int FF=0,int fa=-1){
	int mx=FF,cm=0;
	for(int i=fir[x];i;i=nxt[i]){
		if(fa==dis[i])continue;
		if(F[dis[i]]+1>mx)cm=mx,mx=F[dis[i]]+1;
		else cm=std::max(cm,F[dis[i]]+1);
	}
	for(int i=fir[x];i;i=nxt[i]){
		if(fa==dis[i])continue;
		int df=FF;
		if(F[x]!=F[dis[i]]+1)df=std::max(df,F[x]);
		else df=std::max(df,cF[x]);
		DFS(dis[i],df+1,x);
	}
	int low=1e9;if(S[x]=='1')low=0;
	for(int i=fir[x];i;i=nxt[i])if(fa!=dis[i]&&sz[dis[i]])low=std::min(low,F[dis[i]]+1);
	if(sz[1]-sz[x])low=std::min(low,FF);
	ans+=std::max(0,std::min(mx,cm+2)-low);
}
int main(){
#ifdef XZZSB
	freopen("in.in","r",stdin);
	freopen("out.out","w",stdout);
#endif
	int n=gi(),u,v;
	for(int i=1;i<n;++i)u=gi(),v=gi(),link(u,v),link(v,u);
	scanf("%s",S+1);
	dfs(1);DFS(1);
	printf("%lld\n",ans+1);
	return 0;
}
