#include <iostream> #include <vector> #include <cmath> #include <algorithm> using namespace std; const int MAXN = 5e5 + 7; vector<int> graf[MAXN]; int dp[MAXN][2][2]; //zmiana parent, koncze w v bool color[MAXN]; void dfs(int v, int p) { if (v != p && graf[v].size() == 1) { dp[v][0][0] = 1; dp[v][0][1] = 1; dp[v][1][1] = 5; dp[v][1][0] = 5; return; } int xorr = (graf[v].size()) % 2, optsuma = graf[v].size() + (v == p); if (v == p) xorr ^= 1; xorr ^= color[v]; for (int s : graf[v]) { if (s != p) { dfs(s, v); if (dp[s][0][1] > dp[s][1][1]) xorr ^= 1; optsuma += min(dp[s][0][1], dp[s][1][1]); } } dp[v][0][0] = 1e9; dp[v][0][1] = 1e9; dp[v][1][0] = 1e9; dp[v][1][1] = 1e9; for (int s : graf[v]) { if (s == p) continue; int oh = dp[s][0][1] > dp[s][1][1]; int optsuma2 = optsuma - min(dp[s][0][1], dp[s][1][1]); //cout << "O: " << v << ' ' << s << ' ' << min(dp[s][0][1], dp[s][1][1]) << ' ' << optsuma << ' ' << optsuma2 << ' ' << dp[s][0][0] << ' ' << xorr << ' ' << oh << '\n'; dp[v][0][0] = min(dp[v][0][0], optsuma2 + dp[s][0][0] + min((xorr ^ oh) * (int)1e7, 3) - 1); dp[v][0][0] = min(dp[v][0][0], optsuma2 + dp[s][1][0] + (xorr ^ oh ^ 1) * (int)1e7 - 1); dp[v][1][0] = min(dp[v][1][0], optsuma2 + dp[s][0][0] + (xorr ^ oh ^ 1) * (int)1e7 - 1 + 2); } if (!xorr) dp[v][1][1] = optsuma + 2; else dp[v][0][1] = optsuma; dp[v][0][0] = min(dp[v][0][0], dp[v][0][1]); dp[v][1][0] = min(dp[v][1][0], dp[v][1][1]); // cout << v << ": " << dp[v][0][0] << ' ' << dp[v][0][1] << ' ' << dp[v][1][0] << ' ' << dp[v][1][1] << ' ' << optsuma << ' ' << xorr << '\n'; } int main() { ios_base::sync_with_stdio(0); cin.tie(0); int n, a, b; cin >> n; vector<bool> blocked(n + 1, 0); vector<int> indegree(n + 1, 0); char c; for (int i = 1; i <= n; i++) { cin >> c; color[i] = c - '0'; } for (int i = 0; i < n - 1; i++) { cin >> a >> b; graf[a].push_back(b); graf[b].push_back(a); indegree[a]++; indegree[b]++; } vector<int> kolejka; for (int i = 1; i <= n; i++) { if (indegree[i] == 1 && color[i]) kolejka.push_back(i); } while (kolejka.size()) { int v = kolejka.back(); blocked[v] = 1; kolejka.pop_back(); for (int s : graf[v]) { indegree[s] --; if (indegree[s] == 1 && color[s]) kolejka.push_back(s); } } for (int i = 1; i <= n; i++) { if (blocked[i]) { graf[i].clear(); continue; } vector<int> s2; for (int s : graf[i]) { if (!blocked[s]) s2.push_back(s); } graf[i] = s2; } int ans = 1e9; for (int i = 1; i <= n; i++) { if (blocked[i]) continue; dfs(i, i); //cout << dp[i][0][0] << ' ' << dp[i][0][1] << ' ' << dp[i][1][1] << '\n'; ans = min({ans, dp[i][0][0], dp[i][0][1], dp[i][1][1]}); } cout << ans << '\n'; return 0; }