#include using namespace std; using LL = long long int; #define incII(i, l, r) for(LL i = (l) ; i <= (r); i++) #define incIX(i, l, r) for(LL i = (l) ; i < (r); i++) #define incXI(i, l, r) for(LL i = (l) + 1; i <= (r); i++) #define incXX(i, l, r) for(LL i = (l) + 1; i < (r); i++) #define decII(i, l, r) for(LL i = (r) ; i >= (l); i--) #define decIX(i, l, r) for(LL i = (r) - 1; i >= (l); i--) #define decXI(i, l, r) for(LL i = (r) ; i > (l); i--) #define decXX(i, l, r) for(LL i = (r) - 1; i > (l); i--) #define inc(i, n) incIX(i, 0, n) #define dec(i, n) decIX(i, 0, n) #define inc1(i, n) incII(i, 1, n) #define dec1(i, n) decII(i, 1, n) auto inII = [](auto x, auto l, auto r) { return (l <= x && x <= r); }; auto inIX = [](auto x, auto l, auto r) { return (l <= x && x < r); }; auto inXI = [](auto x, auto l, auto r) { return (l < x && x <= r); }; auto inXX = [](auto x, auto l, auto r) { return (l < x && x < r); }; auto setmin = [](auto & a, auto b) { return (b < a ? a = b, true : false); }; auto setmax = [](auto & a, auto b) { return (b > a ? a = b, true : false); }; auto setmineq = [](auto & a, auto b) { return (b <= a ? a = b, true : false); }; auto setmaxeq = [](auto & a, auto b) { return (b >= a ? a = b, true : false); }; #define PB push_back #define EB emplace_back #define MP make_pair #define MT make_tuple #define FI first #define SE second #define FR front() #define BA back() #define ALL(c) c.begin(), c.end() #define RALL(c) c.rbegin(), c.rend() #define RV(c) reverse(ALL(c)) #define SC static_cast #define SI(c) SC(c.size()) #define SL(c) SC(c.size()) #define RF(e, c) for(auto & e: c) #define SF(c, ...) for(auto & [__VA_ARGS__]: c) #define until(e) while(! (e)) #define if_not(e) if(! (e)) #define ef else if #define UR assert(false) auto * IS = & cin; auto * OS = & cout; array SEQ = { "", " ", "" }; // input template T in() { T a; (* IS) >> a; return a; } // input: tuple template void tin_(istream & is, U & t) { if constexpr(I < tuple_size::value) { is >> get(t); tin_(is, t); } } template istream & operator>>(istream & is, tuple & t) { tin_<0>(is, t); return is; } template auto tin() { return in>(); } // input: array template istream & operator>>(istream & is, array & a) { RF(e, a) { is >> e; } return is; } template auto ain() { return in>(); } // input: multi-dimensional vector template T vin() { T v; (* IS) >> v; return v; } template auto vin(N n, M ... m) { vector(m ...))> v(n); inc(i, n) { v[i] = vin(m ...); } return v; } // input: multi-column (tuple) template void colin_([[maybe_unused]] U & t) { } template void colin_(U & t) { get(t).PB(in()); colin_(t); } template auto colin(int n) { tuple ...> t; inc(i, n) { colin_ ...>, 0, T ...>(t); } return t; } // output void out_([[maybe_unused]] string s) { } template void out_([[maybe_unused]] string s, A && a) { (* OS) << a; } template void out_(string s, A && a, B && ... b) { (* OS) << a << s; out_(s, b ...); } auto outF = [](auto x, auto y, auto z, auto ... a) { (* OS) << x; out_(y, a ...); (* OS) << z << flush; }; auto out = [](auto ... a) { outF("", " " , "\n", a ...); }; auto outS = [](auto ... a) { outF("", " " , " " , a ...); }; auto outL = [](auto ... a) { outF("", "\n", "\n", a ...); }; auto outN = [](auto ... a) { outF("", "" , "" , a ...); }; // output: multi-dimensional vector template ostream & operator<<(ostream & os, vector const & v) { os << SEQ[0]; inc(i, SI(v)) { os << (i == 0 ? "" : SEQ[1]) << v[i]; } return (os << SEQ[2]); } template void vout_(T && v) { (* OS) << v; } template void vout_(T && v, A a, B ... b) { inc(i, SI(v)) { (* OS) << (i == 0 ? "" : a); vout_(v[i], b ...); } } template void vout (T && v, A a, B ... b) { vout_(v, a, b ...); (* OS) << a << flush; } template void voutN(T && v, A a, B ... b) { vout_(v, a, b ...); (* OS) << flush; } // ---- ---- class UnionFind { private: int n, s; vector t; vector> v; public: UnionFind(int nn = 0) { init(nn); } void init(int nn) { n = s = nn; t.clear(); v.clear(); inc(i, n) { t.PB(i); v.EB(1, i); } } int get_n() { return n; } int size() { return s; } int id(int x) { return t.at(x); } const vector> & get_v() { return v; } bool unite(int x, int y) { x = id(x); y = id(y); if(x == y) { return false; } if(v[x].size() < v[y].size()) { swap(x, y); } for(auto & e: v[y]) { v[x].PB(e); t[e] = x; } v[y].clear(); s--; return true; } bool same(int x, int y) { return (id(x) == id(y)); } const vector & operator[](int x) { return v[id(x)]; } friend ostream & operator<<(ostream & os, const UnionFind & uf) { inc(i, uf.n) { os << i << ": "; for(auto & e: uf.v[i]) { os << e << " "; } os << "\n"; } return os; } }; // ---- int main() { auto no = [] { out("No"); exit(0); }; auto n = in(); auto E = vin>(n - 1); vector d(n); SF(E, a, b) { a--; b--; d[a]++; d[b]++; } set se; inc(i, n) { if(d[i] >= 3) { se.insert(i); } } if(SI(se) >= 2) { no(); } if(SI(se) == 1) { int r = * se.begin(); UnionFind uf(n); SF(E, a, b) { if(a == r || b == r) { continue; } uf.unite(a, b); } set se; inc(i, n) { if(i == r) { continue; } se.insert(SI(uf[i])); } if(SI(se) != 1) { no(); } } out("Yes"); }