#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define eb emplace_back
#define pb push_back
#define sz(x) (int) (x).size()
#define mp make_pair
#define f1r(i, a, b) for (int i = (a); i < (b); ++i)
#define f0r(i, a) f1r(i, 0, a)
mt19937 rng((uint32_t) chrono::steady_clock::now().time_since_epoch().count());
template<class T> bool ckmin(T& a, const T& b) { return b < a ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }
#ifdef LOCAL
#define dbg(...) debug(#__VA_ARGS__, __VA_ARGS__);
#else
#define dbg(...) 17;
#endif
template<typename T, typename S> ostream& operator << (ostream &os, const pair<T, S> &p) { return os << "(" << p.first << ", " << p.second << ")"; }
template<typename C, typename T = decay<decltype(*begin(declval<C>()))>, typename enable_if<!is_same<C, string>::value>::type* = nullptr>
ostream& operator << (ostream &os, const C &c) { bool f = true; os << "{"; for (const auto &x : c) { if (!f) os << ", "; f = false; os << x; } return os << "}"; }
template<typename T> void debug(string s, T x) { cerr << s << " = " << x << "\n"; }
template<typename T, typename... Args> void debug(string s, T x, Args... args) { cerr << s.substr(0, s.find(',')) << " = " << x << " | "; debug(s.substr(s.find(',') + 2), args...); }
int main() {
int n;
cin >> n;
vector<vector<int>> adj(n);
f0r(i, n-1) {
int u, v;
cin >> u >> v;
--u, --v;
adj[u].pb(v);
adj[v].pb(u);
}
string s;
cin >> s;
vector<int> dp(n);
int ans = 0;
function<void(int, int)> dfs = [&](int src, int par) {
for (int nxt: adj[src]) {
if (nxt == par) continue;
dfs(nxt, src);
}
if (s[src] == '0') {
int res = 0;
for (int nxt: adj[src]) {
if (nxt == par) continue;
res += max(0, dp[nxt]);
}
ckmax(dp[src], res);
// actually updating ans, assume nothing is actually above
} else {
// no paths
dp[src] = 1;
// at least one path
// under the assumption something's above
int res = -1;
for (int nxt: adj[src]) {
res += max(0, dp[nxt]);
}
ckmax(dp[src], res);
// the node becomes negative
ckmax(ans, res);
// the node does not become negative
res = 0;
for (int nxt: adj[src]) {
if (nxt == par) continue;
ckmax(res, dp[nxt]);
}
ckmax(ans, res + 1);
}
ckmax(ans, dp[src]);
};
dfs(0, -1);
cout << ans << '\n';
return 0;
}
