import std.conv, std.functional, std.range, std.stdio, std.string; import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons; import core.bitop; class EOFException : Throwable { this() { super("EOF"); } } string[] tokens; string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; } int readInt() { return readToken.to!int; } long readLong() { return readToken.to!long; } real readReal() { return readToken.to!real; } bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } } bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } } int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; } int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); } int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); } int N; int[] A, B; int[][] G; int[] sz; int[] dep; void dfsSz(int u, int p) { sz[u] = 1; foreach (i; G[u]) { const v = A[i] ^ B[i] ^ u; if (v != p) { dfsSz(v, u); sz[u] += sz[v]; } } } void dfsDep(int u, int p) { dep[u] = (p == -1) ? 0 : (dep[p] + 1); foreach (i; G[u]) { const v = A[i] ^ B[i] ^ u; if (v != p) { dfsDep(v, u); } } } void main() { try { for (; ; ) { N = readInt(); A = new int[N - 1]; B = new int[N - 1]; foreach (i; 0 .. N - 1) { A[i] = readInt() - 1; B[i] = readInt() - 1; } G = new int[][N]; foreach (i; 0 .. N - 1) { G[A[i]] ~= i; G[B[i]] ~= i; } sz = new int[N]; dfsSz(0, -1); int r = -1; for (int u = 0; ; ) { int vm = -1; foreach (i; G[u]) { const v = A[i] ^ B[i] ^ u; if (vm == -1 || sz[vm] < sz[v]) { vm = v; } } if (vm == -1 || sz[u] >= 2 * sz[vm]) { r = u; break; } else { sz[u] -= sz[vm]; sz[vm] += sz[u]; u = vm; } } debug { writeln("r = ", r); writeln("sz = ", sz); } bool ans; // path int numLeaves; foreach (u; 0 .. N) { if (G[u].length == 1) { ++numLeaves; } } if (numLeaves == 2) { ans = true; } // equidistant from r dep = new int[N]; dfsDep(r, -1); bool same = true; int d = -1; foreach (u; 0 .. N) { if (G[u].length == 1) { if (d == -1) { d = dep[u]; } same = same && (d == dep[u]); } } if (same) { ans = true; } writeln(ans ? "Yes" : "No"); } } catch (EOFException e) { } }