import java.util.Scanner; import java.util.List; import java.util.ArrayList; import java.util.Arrays; public class No1424 { private static int N; private static int[] P; private static List Edge; private static List S; public static void main(String[] args) { Scanner scan = new Scanner(System.in); N = scan.nextInt(); P = new int[N]; Edge = new ArrayList(); for (int i=0; i < N-1; i++) { int v = scan.nextInt() - 1; int u = scan.nextInt() - 1; P[v]++; P[u]++; Edge.add(new Integer[] {v, u}); Edge.add(new Integer[] {u, v}); } scan.close(); S = new ArrayList(); for (int i=0; i < N; i++) { if (P[i] == 1) { S.add(i); } } int res = -1; for (int i=0; i < S.size()-1; i++) { int v = getPath(S.get(i), i); if (v < 0) { System.out.println("No"); return; } else if (res < 0) { res = v; } else if (res != v) { System.out.println("No"); return; } } System.out.println("Yes"); } private static int getPath(int s, int i) { int[] D = new int[N]; Arrays.fill(D, Integer.MAX_VALUE); D[s] = 0; while (true) { boolean update = false; for (Integer[] e : Edge) { if (D[e[0]] != Integer.MAX_VALUE && D[e[1]] > D[e[0]] + 1) { D[e[1]] = D[e[0]] + 1; update = true; } } if (!update) { break; } } int res = -1; for (int e : S.subList(i+1, S.size())) { if (res < 0) { res = D[e]; } else if (res != D[e]) { return -1; } } return res; } }