#include<bits/stdc++.h>
using namespace std;
int d1[200005],d2[200005],tot=0,h[200005],n,x,y,siz[200005],col[200005],fa[200005],d3[200005],d4[200005];
long long ans=0;
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)
{
  int i;	
  siz[x]=col[x],fa[x]=father;
  d3[x]=col[x]?0:1e9;
  for(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,i;
  for(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(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()
{
  int i,j;	
  scanf("%d",&n);
  for(i=1;i<n;i++)
  {
    scanf("%d%d",&x,&y);
    add_edge(x,y);
    add_edge(y,x);
  }
  scanf("%s",ch+1);
  for(i=1;ch[i];i++)
    col[i]=ch[i]-'0';
  dfs1(1,0),dfs2(1,0);
  for(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(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);
  return 0;    
}