//You may miss me deep down
#include <cstdio>
#include <iostream>
using namespace std;
const int M = 200005;
const int inf = 0x3f3f3f3f;
int read()
{
	int x=0,f=1;char c;
	while((c=getchar())<'0' || c>'9') {if(c=='-') f=-1;}
	while(c>='0' && c<='9') {x=(x<<3)+(x<<1)+(c^48);c=getchar();}
	return x*f;
}
int n,tot,f[M],mx[M],se[M],d[M],sz[M];char s[M]; 
struct edge{int v,next;}e[M<<1];long long ans;
void dfs1(int u,int fa)
{
	if(s[u]=='1') d[u]=0,sz[u]=1;
	else d[u]=inf;
	for(int i=f[u];i;i=e[i].next)
	{
		int v=e[i].v;
		if(v==fa) continue;
		dfs1(v,u);sz[u]+=sz[v];
		if(mx[v]+1>mx[u]) se[u]=mx[u],mx[u]=mx[v]+1;
		else if(mx[v]+1>se[u]) se[u]=mx[v]+1;
		if(sz[v]) d[u]=min(d[u],mx[v]+1);
	}
}
void dfs2(int u,int fa)
{
	int up=min(se[u]+1,mx[u]-1);
	if(d[u]<=up) ans+=up-d[u]+1;
	for(int i=f[u];i;i=e[i].next)
	{
		int v=e[i].v;
		if(v==fa) continue;
		int t=(mx[v]+1==mx[u])?se[u]:mx[u];t++;
		if(t>mx[v]) se[v]=mx[v],mx[v]=t;
		else if(t>se[v]) se[v]=t;
		if(sz[1]-sz[v]) d[v]=min(d[v],t);
		dfs2(v,u);
	}
}
signed main()
{
	n=read();
	for(int i=1;i<n;i++)
	{
		int u=read(),v=read();
		e[++tot]=edge{v,f[u]},f[u]=tot;
		e[++tot]=edge{u,f[v]},f[v]=tot;
	}
	scanf("%s",s+1);
	dfs1(1,0);dfs2(1,0);
	printf("%lld\n",ans+1);
}