#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
#define ll long long

struct edge { int t,next; }a[400010];

int head[200010],mx1[200010],mx2[200010],mn[200010],sum[200010],n,tot;
char bo[200010];
ll ans;

inline int rd()
{
	int x=0;char ch=getchar();
	for (;ch<'0'||ch>'9';ch=getchar());
	for (;ch>='0'&&ch<='9';ch=getchar()) x=x*10+ch-'0';
	return x;
}

inline void add(int x,int y) { a[++tot].t=y;a[tot].next=head[x];head[x]=tot; }

inline void dfs(int x,int y)
{
	mn[x]=2123333333;
	if (bo[x]=='1') sum[x]++,mn[x]=0;
	for (int i=head[x];i;i=a[i].next)
	{
		int t=a[i].t;
		if (t==y) continue;
		dfs(t,x);
		sum[x]+=sum[t];
		int hh=mx1[t]+1;
		if (mx1[x]<hh) mx2[x]=mx1[x],mx1[x]=hh;
		else mx2[x]=max(mx2[x],hh);
		if (sum[t]) mn[x]=min(mn[x],hh);
	}
}

inline void dfs1(int x,int y)
{
	for (int i=head[x];i;i=a[i].next)
	{
		int t=a[i].t;
		if (t==y) continue;
		int hh=(mx1[x]==mx1[t]+1)?mx2[x]+1:mx1[x]+1;
		if (mx1[t]<hh) mx2[t]=mx1[t],mx1[t]=hh;
		else mx2[t]=max(mx2[t],hh);
		if (sum[t]<sum[1]) mn[t]=min(mn[t],hh);
		dfs1(t,x);
	}
	int hh=min(mx2[x]+1,mx1[x]-1);
	if (hh>=mn[x]) ans+=hh-mn[x]+1;
}

int main()
{
	n=rd();tot=0;
	for (int i=1;i<n;i++)
	{
		int x=rd(),y=rd();
		add(x,y);add(y,x);
	}
	scanf("%s",bo+1);
	ans=0LL;dfs(1,0);dfs1(1,0);
	printf("%lld\n",ans+1);
	return 0;
}