#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=4e5+10;
int n,w[N],head[N],nxt[N];
void add(int f,int t){
	static int cnt=0;
	w[++cnt]=t;
	nxt[cnt]=head[f];
	head[f]=cnt;
}
char tp[N];
long long ans;
int mp[N],cp[N],up[N];
void dfs(int x,int fa){
    for (int i=head[x];i;i=nxt[i]){
        int v=w[i];
        if (v==fa) continue;
        dfs(v,x);
        if (up[v]>up[mp[x]]) cp[x]=mp[x],mp[x]=v;else
        if (up[v]>up[cp[x]]) cp[x]=v;
    }
    up[x]=up[mp[x]]+1;
}
int Max[N],Min[N];
void getmax(int x,int fa){
    for (int i=head[x];i;i=nxt[i]){
        int v=w[i];
        if (v==fa) continue;
        up[x]=up[v==mp[x]?cp[x]:mp[x]]+1;
        Max[v]=min(up[v]+1,up[x]);
        if (up[x]>up[mp[v]]) cp[v]=mp[v],mp[v]=x;else
        if (up[x]>up[cp[v]]) cp[v]=x;
        up[v]=up[mp[v]]+1;
        getmax(v,x);
        up[v]=up[x==mp[v]?cp[v]:mp[v]]+1;
        up[x]=up[mp[x]]+1;
    }
}
int ma[N],ci[N];
void DFS(int x,int fa){
	if (tp[x]=='0') ma[x]=ci[x]=1e9;else ma[x]=ci[x]=1;
	for (int i=head[x];i;i=nxt[i]){
		int v=w[i];
		if (v==fa) continue;
		up[x]=up[v==mp[x]?cp[x]:mp[x]]+1;
		up[v]=up[mp[v]]+1;
		DFS(v,x);
		up[v]=up[x==mp[v]?cp[v]:mp[v]]+1;
		if (tp[x]=='0'&&ma[v]<1e9){
			int R=max(ma[v],min(up[v]+2,up[x]+1));
			R=max(min(R,up[v])+1,min(R-1,up[x]));
			if (R<ma[x]) ci[x]=ma[x],ma[x]=R;else ci[x]=min(ci[x],R);
		}
		up[x]=up[mp[x]]+1;
	}
}
void getmin(int x,int fa){
	Min[x]=ma[x];
	if (Max[x]>=Min[x]) ans+=Max[x]-Min[x]+1;
	for (int i=head[x];i;i=nxt[i]){
		int v=w[i];
		if (v==fa) continue;
		up[x]=up[v==mp[x]?cp[x]:mp[x]]+1;
		if (tp[v]=='0'&&ma[x]<1e9){
			int R=max(ma[x],min(up[x]+2,up[v]+1));
			R=max(min(R,up[x])+1,min(R-1,up[v]));
			if (R<ma[v]) ci[v]=ma[v],ma[v]=R;else ci[v]=min(ci[v],R);
		}
		up[v]=up[mp[v]]+1;
		getmin(v,x);
		up[v]=up[x==mp[v]?cp[v]:mp[v]]+1;
        up[x]=up[mp[x]]+1;
	}
}
int main()
{
	scanf("%d",&n);
	for (int i=1;i<n;i++){
		int u,v;
		scanf("%d%d",&u,&v);
		add(u,v);add(v,u);
	}
	scanf("%s",tp+1);
	int root=0;
	for (int i=1;i<=n;i++)
	if (tp[i]=='1') root=i;
	dfs(root,0);getmax(root,0);Max[root]=up[root];
	DFS(root,0);getmin(root,0);
	//for (int i=1;i<=n;i++) printf("[%d,%d]\n",Min[i],Max[i]);
	printf("%lld\n",ans);
	return 0;
}