#include<bits/stdc++.h>
#define pb push_back

using namespace std;

const int N=200005;

int n,mx[N],se[N],low[N],z[N];
vector<int>e[N];
char s[N];
long long ans;

inline void upd(int x,int u){if(u>mx[x])se[x]=mx[x],mx[x]=u;else if(u>se[x])se[x]=u;}
void dfs1(int x,int fa){
	low[x]=N;
	if(s[x]=='1')low[x]=0,z[x]=1;
	for(int v:e[x])if(v!=fa){
		dfs1(v,x);int d=mx[v]+1;upd(x,d);
		if(z[v])low[x]=min(low[x],d),z[x]+=z[v];
	}
}
void dfs2(int x,int fa){
	if(fa){
		int d=mx[x]+1==mx[fa]?se[fa]+1:mx[fa]+1;
		upd(x,d);if(z[1]>z[x])low[x]=min(low[x],d);
	}
	for(int v:e[x])if(v!=fa)dfs2(v,x);
	int l=low[x],r=min(se[x]+1,mx[x]-1);
	if(l<=r)ans+=r-l+1;
}

int main(){
	scanf("%d",&n);
	for(int i=1,u,v;i<n;i++)scanf("%d%d",&u,&v),e[u].pb(v),e[v].pb(u);
	scanf("%s",s+1);
	dfs1(1,0);dfs2(1,0);
	printf("%lld\n",ans+1);
	return 0;
}