#include <cstdio>
#include <iostream>
#include <algorithm>
using namespace std;
const int Q=1<<18;
int las[Q],e[Q<<1],nn[Q<<1],inc=0;
void ins(int x,int y)
{
	e[++inc]=y;
	nn[inc]=las[x];
	las[x]=inc;
}
#define ll long long 
ll als=0;
int up[Q],down[Q];
int fa[Q],si[Q],mlen[2][Q],id[Q],flen[Q];
char s[Q];
void dfs(int x)
{
	si[x]=s[x]-'0';
	for(int t=las[x];t;t=nn[t]){
		int y=e[t];
		if(y==fa[x])continue;
		fa[y]=x;
		dfs(y);
		si[x]+=si[y];
		int v=mlen[0][y]+1;
		if(v>mlen[0][x])id[x]=y,mlen[1][x]=mlen[0][x],mlen[0][x]=v;
		else mlen[1][x]=max(mlen[1][x],v);
	}
}
const int inf=998244353;
void ddfs(int x)
{
	if(fa[x]){
		int fat=fa[x];
		if(id[fat]==x)
			flen[x]=mlen[1][fat]+1;
		else flen[x]=mlen[0][fat]+1;
		flen[x]=max(flen[x],flen[fat]+1);
	}
	else flen[x]=-inf;
	int u=max(flen[x],mlen[0][x])-1,d=inf;
	for(int t=las[x];t;t=nn[t]){
		int y=e[t];
		if(y==fa[x]){
			u=min(u,mlen[0][x]+1);
			if(si[1]-si[x])
				d=min(d,flen[x]);
		}
		else{
			if(y==id[x])u=min(u,max(flen[x],mlen[1][x])+1);
			else u=min(u,max(flen[x],mlen[0][x])+1);
			if(si[y])d=min(d,mlen[0][y]+1);
		}
	}
	if(s[x]=='1')d=0;
	als+=max(0LL,(ll)u-d+1);
	for(int t=las[x];t;t=nn[t]){
		int y=e[t];
		if(y==fa[x])continue;
		ddfs(y);
	}
}
int main()
{
	int n;
	scanf("%d",&n);
	for(int i=1,x,y;i<n;i++)
		scanf("%d%d",&x,&y),ins(x,y),ins(y,x);
	scanf("%s",s+1);
	dfs(1);
	ddfs(1);
	printf("%lld\n",als+1LL);
	return 0;
}