#include<bits/stdc++.h>
using namespace std;
#define ff first
#define ss second
#define pb push_back
#define mp make_pair
typedef long long LL;
typedef unsigned long long uLL;
typedef pair<int,int> pii;

const int maxn=200111;
const int inf=0x3f3f3f3f;

vector<int> g[maxn];
int n,d[maxn],down[maxn],up[maxn],fa[maxn],near[maxn],near2[maxn],d2[maxn];
char s[maxn];

void dfs(int x,int f)
{
	down[x]=0;fa[x]=f;
	if(s[x]=='0')near[x]=inf;else near[x]=0;
	for(int i=0;i<(int)g[x].size();i++)if(g[x][i]!=f)
	{
		dfs(g[x][i],x);
		down[x]=max(down[x],down[g[x][i]]+1);
		near[x]=min(near[x],near[g[x][i]]+1);
	}
}
void dfs2(int x)
{
	if(s[x]=='1')near2[x]=0;
	int mx=up[x]+1,mx2,mn=near2[x]+1;
	for(int i=0;i<(int)g[x].size();i++)if(g[x][i]!=fa[x])
	{
		up[g[x][i]]=mx;
		near2[g[x][i]]=mn;
		mn=min(mn,near[g[x][i]]+2);
		mx=max(mx,down[g[x][i]]+2);
	}
	mx=0;mn=inf;
	for(int i=(int)g[x].size()-1;i>=0;i--)if(g[x][i]!=fa[x])
	{
		up[g[x][i]]=max(up[g[x][i]],mx);
		near2[g[x][i]]=min(near2[g[x][i]],mn);
		mx=max(mx,down[g[x][i]]+2);
		mn=min(mn,near[g[x][i]]+2);
		dfs2(g[x][i]);
	}
	
	mx=mx2=0;
	d2[x]=inf;if(s[x]=='1')d2[x]=0;
	for(int i=0;i<(int)g[x].size();i++)
	{
		int cur;if(g[x][i]==fa[x])cur=up[x];else cur=down[g[x][i]]+1;
		int cur2;if(g[x][i]==fa[x])cur2=near2[x];else cur2=near[g[x][i]]+1;
		if(cur>mx)
		{
			mx2=mx;
			mx=cur;
		}
		else if(cur>mx2)mx2=cur;
		d2[x]=min(d2[x],max(cur2,cur));
	}
	d[x]=min(mx-1,mx2+1);
	
//	printf("x= %d mx= %d mx2= %d d= %d\n",x,mx,mx2,d[x]);
}

int main()
{
	scanf("%d",&n);
	for(int i=1,u,v;i<n;i++)
	{
		scanf("%d%d",&u,&v);
		g[u].pb(v);g[v].pb(u);
	}
	scanf("%s",s+1);
	
	dfs(1,0);near2[1]=inf;dfs2(1);
	
	LL ans=1;
	for(int i=1;i<=n;i++)ans+=max(0,d[i]-d2[i]+1);
	printf("%lld\n",ans);
	return 0;
}