#include <iostream>
#include <cstdlib>
#include <cstdio>
#define N 200011
#define INF 0x7f7f7f7f
#define int long long
using namespace std;
int L[N],R[N],maxx1[N],maxx2[N],fa[N],siz[N],n,indexx[N],tot,Mark[N],ans;
char s[N];
struct apple{
	int v,nxt;
}edge[N*4];
void addedge(int x,int y){
	edge[++tot].v=y;
	edge[tot].nxt=indexx[x];
	indexx[x]=tot;
}
void dfs1(int u,int f){
	if(Mark[u]){
		siz[u]=1;
		L[u]=0;
	}
	else L[u]=INF;
	fa[u]=f;
	maxx1[u]=0;
	maxx2[u]=-INF;
	int t=indexx[u],vv;
	while(t){
		vv=edge[t].v;
		if(vv!=f){
			dfs1(vv,u);
			siz[u]+=siz[vv];
			if(maxx1[vv]+1>maxx1[u]){
				maxx2[u]=maxx1[u];
				maxx1[u]=maxx1[vv]+1;
			}
			else if(maxx1[vv]+1>maxx2[u]){
				maxx2[u]=maxx1[vv]+1;
			}
			if(siz[vv]) L[u]=min(L[u],maxx1[vv]+1);
		}
		t=edge[t].nxt;
	}
}
void dfs(int u){
	int temp;
	R[u]=min(maxx1[u]-1,maxx2[u]+1);
	if(R[u]>=L[u]) ans+=R[u]-L[u]+1;
	int t=indexx[u],vv;
	while(t){
		vv=edge[t].v;
		if(vv!=fa[u]){
			if(maxx1[u]==maxx1[vv]+1){
				temp=maxx2[u]+1;
			}
			else temp=maxx1[u]+1;
			if(temp>maxx1[vv]) maxx2[vv]=maxx1[vv],maxx1[vv]=temp;
			else if(temp>maxx2[vv]) maxx2[vv]=temp;
			if(siz[1]-siz[vv]) L[vv]=min(L[vv],temp);
			dfs(vv);
		}
		t=edge[t].nxt;
	}
}
signed main(){
	int x,y;
	scanf("%lld",&n);
	for(int i=1;i<n;i++){
		scanf("%lld%lld",&x,&y);
		addedge(x,y);
		addedge(y,x);
	}
	scanf("%s",s+1);
	for(int i=1;i<=n;i++) Mark[i]=s[i]-'0';
	dfs1(1,0);
	dfs(1);
	printf("%lld",ans+1);
	return 0;
}