#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N=210000;
int n,tot;
char s[N];
int head[N],nex[N<<1],to[N<<1];
int f1[N],f2[N],g[N],lb[N],size[N];
ll ans;
void add(int x,int y)
{
	tot++;
	nex[tot]=head[x];head[x]=tot;
	to[tot]=y;
}
void upd(int &x,int &y,int z)
{
	if(z>x)y=x,x=z;
	else if(z>y)y=z;
}
void dfs1(int x,int y)
{
	size[x]=s[x]-'0';
	for(int i=head[x],t;i;i=nex[i])if((t=to[i])!=y)
	{
		dfs1(t,x);
		size[x]+=size[t];
		upd(f1[x],f2[x],f1[t]+1);
		if(size[t])
			lb[x]=min(lb[x],f1[t]+1);
	}
}
void dfs2(int x,int y)
{
	for(int i=head[x],t,d;i;i=nex[i])if((t=to[i])!=y)
	{
		g[t]=max(g[x],f1[t]+1==f1[x] ? f2[x] : f1[x])+1;
		if(size[t]!=size[1])
			lb[t]=min(lb[t],g[t]);
		dfs2(t,x);
	}
}
int main()
{
	//freopen("tt.in","r",stdin);
	scanf("%d",&n);
	for(int i=1,x,y;i<n;i++)
	{
		scanf("%d%d",&x,&y);
		add(x,y);add(y,x);
	}
	scanf("%s",s+1);
	for(int i=1;i<=n;i++)
		if(s[i]=='0')lb[i]=n+1;
	dfs1(1,0);
	dfs2(1,0);
	for(int i=1;i<=n;i++)
	{
		upd(f1[i],f2[i],g[i]);
		ans+=max(0,min(f1[i]-1,f2[i]+1)-lb[i]+1);
	}
	printf("%lld\n",ans+1);
	return 0;
}
