#include <bits/stdc++.h> using namespace std; void Init() { ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr); } typedef long long ll; const int MAXN = 200000 + 5; const ll INF = (ll)9e18; int n; vector<int> g[MAXN]; int initState[MAXN]; // 0 = off, 1 = on ll dp[MAXN][2][2]; // dp[v][parentPress][pressV] int parentArr[MAXN]; void Input() { cin >> n; for (int i = 1; i <= n; ++i) { g[i].clear(); initState[i] = 0; } for (int i = 0; i < n - 1; ++i) { int u, v; cin >> u >> v; g[u].push_back(v); g[v].push_back(u); } // read states: either a single string "0101..." or n integers string token; cin >> token; if ((int)token.size() == n) { for (int i = 1; i <= n; ++i) initState[i] = token[i-1] - '0'; } else { // token is first number initState[1] = stoi(token); for (int i = 2; i <= n; ++i) cin >> initState[i]; } } void dfs(int v, int p) { parentArr[v] = p; for (int to : g[v]) if (to != p) dfs(to, v); // for pressV = 0 and pressV = 1 compute tmp_even/tmp_odd for (int parentPress = 0; parentPress <= 1; ++parentPress) { for (int pressV = 0; pressV <= 1; ++pressV) { // compute tmp for this pressV: ll even = 0; ll odd = INF; for (int to : g[v]) { if (to == p) continue; ll cand_even = min( (even >= INF ? INF : even + dp[to][pressV][0]), (odd >= INF ? INF : odd + dp[to][pressV][1]) ); ll cand_odd = min( (odd >= INF ? INF : odd + dp[to][pressV][0]), (even >= INF ? INF : even + dp[to][pressV][1]) ); even = cand_even; odd = cand_odd; } int toggles = (parentPress + pressV) & 1; // parity ignoring children int needParity = initState[v] ^ toggles; // children parity required: s ^ parentPress ^ pressV if (needParity == 0) { dp[v][parentPress][pressV] = (pressV ? 1LL : 0LL) + even; } else { dp[v][parentPress][pressV] = (pressV ? 1LL : 0LL) + odd; } if (dp[v][parentPress][pressV] > INF) dp[v][parentPress][pressV] = INF; } } } void Bai() { // choose root = 1 dfs(1, 0); ll ans = min(dp[1][0][0], dp[1][0][1]); if (ans >= INF/2) cout << -1 << '\n'; else cout << ans << '\n'; } int main() { Init(); Input(); Bai(); return 0; }