#line 1 "/home/siro53/kyo-pro/compro_library/template/template.cpp" #include using namespace std; template inline bool chmax(T &a, T b) { if(a < b) { a = b; return 1; } return 0; } template inline bool chmin(T &a, T b) { if(a > b) { a = b; return 1; } return 0; } #define DEBUG #ifdef DEBUG template ostream &operator<<(ostream &os, const pair &p) { os << '(' << p.first << ',' << p.second << ')'; return os; } template ostream &operator<<(ostream &os, const vector &v) { os << '{'; for(int i = 0; i < (int)v.size(); i++) { if(i) { os << ','; } os << v[i]; } os << '}'; return os; } void debugg() { cerr << endl; } template void debugg(const T &x, const Args &... args) { cerr << " " << x; debugg(args...); } #define debug(...) \ cerr << __LINE__ << " [" << #__VA_ARGS__ << "]: ", debugg(__VA_ARGS__) #define dump(x) cerr << __LINE__ << " " << #x << " = " << (x) << endl #else #define debug(...) (void(0)) #define dump(x) (void(0)) #endif struct Setup { Setup() { cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(15); } } __Setup; using ll = long long; #define ALL(v) (v).begin(), (v).end() #define RALL(v) (v).rbegin(), (v).rend() #define FOR(i, a, b) for(int i = (a); i < int(b); i++) #define REP(i, n) FOR(i, 0, n) const int INF = 1 << 30; const ll LLINF = 1LL << 60; constexpr int MOD = 1000000007; const int dx[4] = {1, 0, -1, 0}; const int dy[4] = {0, 1, 0, -1}; //------------------------------------- #line 1 "/home/siro53/kyo-pro/compro_library/graph/tree_diameter.hpp" vector get_diameter_path(const vector> &G) { int n = (int)G.size(); vector depth(n), par(n); auto dfs = [&](auto &&dfs, int v, int p, int d) -> void { depth[v] = d; par[v] = p; for(const int &u : G[v]) { if(u != p) { dfs(dfs, u, v, d + 1); } } }; dfs(dfs, 0, -1, 0); int from = max_element(ALL(depth)) - depth.begin(); dfs(dfs, from, -1, 0); int to = max_element(ALL(depth)) - depth.begin(); vector res; int now = to; while(now != from) { res.emplace_back(now); now = par[now]; } res.emplace_back(now); return res; } #line 3 "c.cpp" int N; vector> G; int main() { cin >> N; G.resize(N); REP(i, N-1) { int a, b; cin >> a >> b; a--; b--; G[a].push_back(b); G[b].push_back(a); } vector rs; REP(i, N) { if(G[i].size() >= 3) { rs.push_back(i); } } if(rs.size() >= 2) { cout<<"No\n"; return 0; }else if(rs.empty()) { cout<<"Yes\n"; return 0; } set se; auto check = [&](auto self, int u, int p, int d) -> void { bool f = true; for(int v: G[u]) { if(v == p) continue; self(self, v, u, d+1); f = 0; } if(f) se.insert(d); }; check(check, rs[0], -1, 0); if(se.size() == 1) { cout << "Yes\n"; }else{ cout << "No\n"; } }