#include <bits/stdc++.h>
using namespace std;

using ll=long long;
#define int ll

#define rng(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,b) rng(i,0,b)
#define gnr(i,a,b) for(int i=int(b)-1;i>=int(a);i--)
#define per(i,b) gnr(i,0,b)
#define pb push_back
#define eb emplace_back
#define a first
#define b second
#define bg begin()
#define ed end()
#define all(x) x.bg,x.ed
#ifdef LOCAL
#define dmp(x) cerr<<__LINE__<<" "<<#x<<" "<<x<<endl
#else
#define dmp(x) void(0)
#endif

template<class t,class u> void chmax(t&a,u b){if(a<b)a=b;}
template<class t,class u> void chmin(t&a,u b){if(b<a)a=b;}

template<class t> using vc=vector<t>;
template<class t> using vvc=vc<vc<t>>;

using pi=pair<int,int>;
using vi=vc<int>;

template<class t,class u>
ostream& operator<<(ostream& os,const pair<t,u>& p){
	return os<<"{"<<p.a<<","<<p.b<<"}";
}

template<class t> ostream& operator<<(ostream& os,const vc<t>& v){
	os<<"{";
	for(auto e:v)os<<e<<",";
	return os<<"}";
}

#define mp make_pair
#define mt make_tuple
#define one(x) memset(x,-1,sizeof(x))
#define zero(x) memset(x,0,sizeof(x))
#ifdef LOCAL
void dmpr(ostream&os){os<<endl;}
template<class T,class... Args>
void dmpr(ostream&os,const T&t,const Args&... args){
	os<<t<<" ";
	dmpr(os,args...);
}
#define dmp2(...) dmpr(cerr,"Line:",__LINE__,##__VA_ARGS__)
#else
#define dmp2(...) void(0)
#endif

using uint=unsigned;
using ull=unsigned long long;

template<int i,class T>
void print_tuple(ostream&,const T&){
}

template<int i,class T,class H,class ...Args>
void print_tuple(ostream&os,const T&t){
	if(i)os<<",";
	os<<get<i>(t);
	print_tuple<i+1,T,Args...>(os,t);
}

template<class ...Args>
ostream& operator<<(ostream&os,const tuple<Args...>&t){
	os<<"{";
	print_tuple<0,tuple<Args...>,Args...>(os,t);
	return os<<"}";
}

void print(ll x,int suc=1){
	cout<<x;
	if(suc==1)
		cout<<"\n";
	if(suc==2)
		cout<<" ";
}

ll read(){
	ll i;
	cin>>i;
	return i;
}

vi readvi(int n,int off=0){
	vi v(n);
	rep(i,n)v[i]=read()+off;
	return v;
}

template<class T>
void print(const vector<T>&v,int suc=1){
	rep(i,v.size())
		print(v[i],i==int(v.size())-1?suc:2);
}

string readString(){
	string s;
	cin>>s;
	return s;
}

template<class T>
T sq(const T& t){
	return t*t;
}

//#define CAPITAL
void yes(bool ex=true){
	#ifdef CAPITAL
	cout<<"YES"<<endl;
	#else
	cout<<"Yes"<<endl;
	#endif
	if(ex)exit(0);
}
void no(bool ex=true){
	#ifdef CAPITAL
	cout<<"NO"<<endl;
	#else
	cout<<"No"<<endl;
	#endif
	if(ex)exit(0);
}

constexpr ll ten(int n){
	return n==0?1:ten(n-1)*10;
}

const ll infLL=LLONG_MAX/3;

#ifdef int
const int inf=infLL;
#else
const int inf=INT_MAX/2-100;
#endif

int topbit(signed t){
	return t==0?-1:31-__builtin_clz(t);
}
int topbit(ll t){
	return t==0?-1:63-__builtin_clzll(t);
}
int botbit(signed a){
	return a==0?32:__builtin_ctz(a);
}
int botbit(ll a){
	return a==0?64:__builtin_ctzll(a);
}
int popcount(signed t){
	return __builtin_popcount(t);
}
int popcount(ll t){
	return __builtin_popcountll(t);
}
bool ispow2(int i){
	return i&&(i&-i)==i;
}
int mask(int i){
	return (int(1)<<i)-1;
}

bool inc(int a,int b,int c){
	return a<=b&&b<=c;
}

template<class t> void mkuni(vc<t>&v){
	sort(all(v));
	v.erase(unique(all(v)),v.ed);
}

ll rand_int(ll l, ll r) { //[l, r]
	#ifdef LOCAL
	static mt19937_64 gen;
	#else
    static random_device rd;
    static mt19937_64 gen(rd());
    #endif
    return uniform_int_distribution<ll>(l, r)(gen);
}

template<class t>
int lwb(const vc<t>&v,const t&a){
	return lower_bound(all(v),a)-v.bg;
}

const int nmax=200010;

vi t[nmax];
int far[nmax];
int len[nmax];

void dfs1(int v,int p){
	for(auto c:t[v])if(c!=p){
		dfs1(c,v);
		chmax(len[v],len[c]+1);
	}
}

void dfs2(int v,int p,int d,vc<tuple<int,int,int,int>>&es){
	vi z{d};
	for(auto c:t[v])if(c!=p){
		z.pb(len[c]+1);
	}
	sort(all(z),greater<int>());
	far[v]=z[0];
	for(auto c:t[v])if(c!=p){
		int w=z[0];
		if(w==len[c]+1)
			w=z[1];
		es.eb(c,v,len[c],w);
		dfs2(c,v,w+1,es);
	}
}

signed main(){
	cin.tie(0);
	ios::sync_with_stdio(0);
	cout<<fixed<<setprecision(20);
	
	int n;cin>>n;
	rep(_,n-1){
		int a,b;cin>>a>>b;
		a--;b--;
		t[a].pb(b);
		t[b].pb(a);
	}
	
	dfs1(0,-1);
	
	vc<tuple<int,int,int,int>> es;
	dfs2(0,-1,0,es);
	
	vi dist(n,inf);
	priority_queue<pi,vc<pi>,greater<pi>> pq;
	auto rc=[&](int i,int d){
		if(dist[i]<=d)return;
		dist[i]=d;
		pq.emplace(d,i);
	};
	
	string s;cin>>s;
	rep(i,n)if(s[i]=='1')
		rc(i,0);
	
	vvc<tuple<int,int,int>> g(n);
	for(auto e:es){
		int u,v,a,b;tie(u,v,a,b)=e;
		if(a>b){
			swap(a,b);
			swap(u,v);
		}
		
		g[u].eb(0,v,a);
		g[v].eb(1,u,a);
	}
	
	dmp(es);
	
	while(pq.size()){
		int v,d;tie(d,v)=pq.top();pq.pop();
		if(dist[v]!=d)continue;
		
		for(auto e:g[v]){
			int k,to,a;tie(k,to,a)=e;
			rc(to,k==0?max(d-1,a+1):max(d+1,a+2));
		}
	}
	
	dmp(dist);
	
	int ans=1;
	rep(i,n){
		if(dist[i]<far[i]){
			ans+=far[i]-dist[i];
		}
	}
	for(auto e:es){
		int u,v,a,b;tie(u,v,a,b)=e;
		if(a>b){
			swap(a,b);
			swap(u,v);
		}
		
		int x=max(a+1,dist[v]);
		int y=max(a+2,dist[u]);
		ans-=max(int(0),min(far[v]-x,far[u]-y));
	}
	
	cout<<ans<<endl;
}


Measured memory_bytes: 65900