#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include using namespace std; typedef long long ll; typedef vector vl; typedef vector> vvl; typedef pair P; #define rep(i, n) for(ll i = 0; i < n; i++) #define exrep(i, a, b) for(ll i = a; i <= b; i++) #define out(x) cout << x << endl #define exout(x) printf("%.10f\n", x) #define chmax(x, y) x = max(x, y) #define chmin(x, y) x = min(x, y) #define all(a) a.begin(), a.end() #define rall(a) a.rbegin(), a.rend() #define pb push_back #define re0 return 0 const ll mod = 1000000007; const ll INF = 1e16; struct Edge { ll to, cost; Edge(ll to, ll cost): to(to), cost(cost) {} }; int main() { ll n; cin >> n; vector> G(n); vl deg(n); rep(i, n-1) { ll a, b; cin >> a >> b; a--; b--; G[a].emplace_back(b, 1); G[b].emplace_back(a, 1); deg[a]++; deg[b]++; } vl dist(n, -1); // dist[v] : 頂点vの根からの距離 queue Q; const ll root = 0; dist[root] = 0; Q.push(root); while(!Q.empty()) { ll v = Q.front(); Q.pop(); for(Edge e : G[v]) { if(dist[e.to] == -1) { dist[e.to] = dist[v] + e.cost; Q.push(e.to); } } } bool ok = true; ll x = -1; rep(v, n) { if(v != root && deg[v] == 1) { if(x == -1) { x = dist[v]; } else if(x != dist[v]) { ok = false; } } } if(ok) { out("Yes"); } else { out("No"); } re0; }