#ifndef CPL_TEMPLATE
#define CPL_TEMPLATE
/*
Normie's Template v2.5
Changes:
Added warning against using pragmas on USACO.
*/
// Standard library in one include.
#include <bits/stdc++.h>
using namespace std;
// ordered_set library.
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
#define ordered_set(el) tree<el,null_type,less<el>,rb_tree_tag,tree_order_statistics_node_update>
// AtCoder library. (Comment out these two lines if you're not submitting in AtCoder.) (Or if you want to use it in other judges, run expander.py first.)
//#include <atcoder/all>
//using namespace atcoder;
//Pragmas (Comment out these three lines if you're submitting in szkopul or USACO.)
//File I/O.
#define FILE_IN "cseq.inp"
#define FILE_OUT "cseq.out"
#define ofile freopen(FILE_IN,"r",stdin);freopen(FILE_OUT,"w",stdout)
//Fast I/O.
#define fio ios::sync_with_stdio(0);cin.tie(0)
#define nfio cin.tie(0)
#define endl "\n"
//Order checking.
#define ord(a,b,c) ((a>=b)and(b>=c))
//min/max redefines, so i dont have to resolve annoying compile errors.
#define min(a,b) (((a)<(b))?(a):(b))
#define max(a,b) (((a)>(b))?(a):(b))
// Fast min/max assigns to use with AVX.
// Requires g++ 9.2.0.
template<typename T>
__attribute__((always_inline)) void chkmin(T& a, const T& b) {
a=(a<b)?a:b;
}
template<typename T>
__attribute__((always_inline)) void chkmax(T& a, const T& b) {
a=(a>b)?a:b;
}
//Constants.
#define MOD (ll(998244353))
#define MAX 300001
#define mag 320
const long double PI=3.14159265358979;
//Pairs and 3-pairs.
#define p1 first
#define p2 second.first
#define p3 second.second
#define fi first
#define se second
#define pii(element_type) pair<element_type,element_type>
#define piii(element_type) pair<element_type,pii(element_type)>
//Quick power of 2.
#define pow2(x) (ll(1)<<x)
//Short for-loops.
#define ff(i,__,___) for(int i=__;i<=___;i++)
#define rr(i,__,___) for(int i=__;i>=___;i--)
//Typedefs.
#define bi BigInt
typedef long long ll;
typedef long double ld;
typedef short sh;
// Binpow and stuff
ll BOW(ll a, ll x, ll p)
{
if (!x) return 1;
ll res=BOW(a,x/2,p);
res*=res;
res%=p;
if (x%2) res*=a;
return res%p;
}
ll INV(ll a, ll p)
{
return BOW(a,p-2,p);
}
//---------END-------//
#endif
vector<int> gt[200001];
int n,m,i,j,k,t,t1,u,v,a,b;
int dp[200001][2];
string gen;
void calc(int x, int p) {
int cur,a,b,c;
vector<int> ch;
for (auto g : gt[x]) if (g-p) {
calc(g,x);
ch.push_back(g);
}
if (gen[x]=='0') {
cur=0; a=0; b=0;
for (auto g : ch) {
a+=dp[g][1];
b=max(b,dp[g][0]);
}
dp[x][0]=max(a,b);
dp[x][1]=a;
}
else {
cur=1;
dp[x][cur]=1;
a=0; b=0;
for (auto g : ch) {
a+=dp[g][1];
b=max(b,dp[g][1]);
}
dp[x][cur]=max(dp[x][cur],-1+a);
// dp[x][cur]=max(dp[x][cur],b);
cur=0;
dp[x][cur]=-1e9;
a=0; b=0; c=0;
for (auto g : ch) {
a+=dp[g][1];
b=max(b,dp[g][0]);
c=max(c,dp[g][1]);
}
dp[x][cur]=max(dp[x][cur],-1+a);
dp[x][cur]=max(dp[x][cur],b);
dp[x][cur]=max(dp[x][cur],c+1);
}
// cout<<"A\n";
// cout<<x<<' '<<gen[x]<<' '<<dp[x][0]<<' '<<dp[x][1]<<endl;
// for (auto g : ch) cout<<g<<' ';
// cout<<endl;
}
int main()
{
fio;
cin>>n;
for (i=1;i<n;i++) {
cin>>a>>b; a--; b--;
gt[a].push_back(b);
gt[b].push_back(a);
}
cin>>gen;
calc(0,-1);
cout<<dp[0][0];
}
