package contest190322; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Arrays; import java.util.InputMismatchException; public class C { InputStream is; PrintWriter out; String INPUT = ""; void solve() { int n = ni(); int[] from = new int[n - 1]; int[] to = new int[n - 1]; for (int i = 0; i < n - 1; i++) { from[i] = ni() - 1; to[i] = ni() - 1; } int[][] g = packU(n, from, to); int[] dia = diameter(g); out.println(n-1-dia[0]); } public static int[] diameter(int[][] g) { int n = g.length; int f0 = -1, f1 = -1, d01 = -1; int[] q = new int[n]; boolean[] ved = new boolean[n]; { int qp = 0; q[qp++] = 0; ved[0] = true; for(int i = 0;i < qp;i++){ int cur = q[i]; for(int e : g[cur]){ if(!ved[e]){ ved[e] = true; q[qp++] = e; continue; } } } f0 = q[n-1]; } { int[] d = new int[n]; int qp = 0; Arrays.fill(ved, false); q[qp++] = f0; ved[f0] = true; for(int i = 0;i < qp;i++){ int cur = q[i]; for(int e : g[cur]){ if(!ved[e]){ ved[e] = true; q[qp++] = e; d[e] = d[cur] + 1; continue; } } } f1 = q[n-1]; d01 = d[f1]; } return new int[]{d01, f0, f1}; } public static int[][] parents3(int[][] g, int root) { int n = g.length; int[] par = new int[n]; Arrays.fill(par, -1); int[] depth = new int[n]; depth[0] = 0; int[] q = new int[n]; q[0] = root; for (int p = 0, r = 1; p < r; p++) { int cur = q[p]; for (int nex : g[cur]) { if (par[cur] != nex) { q[r++] = nex; par[nex] = cur; depth[nex] = depth[cur] + 1; } } } return new int[][] { par, q, depth }; } static int[][] packU(int n, int[] from, int[] to) { int[][] g = new int[n][]; int[] p = new int[n]; for (int f : from) p[f]++; for (int t : to) p[t]++; for (int i = 0; i < n; i++) g[i] = new int[p[i]]; for (int i = 0; i < from.length; i++) { g[from[i]][--p[from[i]]] = to[i]; g[to[i]][--p[to[i]]] = from[i]; } return g; } void run() throws Exception { is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes()); out = new PrintWriter(System.out); long s = System.currentTimeMillis(); solve(); out.flush(); if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){ // @Override // public void run() { // long s = System.currentTimeMillis(); // solve(); // out.flush(); // if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // } // }; // t.start(); // t.join(); } public static void main(String[] args) throws Exception { new C().run(); } private byte[] inbuf = new byte[1024]; public int lenbuf = 0, ptrbuf = 0; private int readByte() { if(lenbuf == -1)throw new InputMismatchException(); if(ptrbuf >= lenbuf){ ptrbuf = 0; try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); } if(lenbuf <= 0)return -1; } return inbuf[ptrbuf++]; } private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); } private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; } private double nd() { return Double.parseDouble(ns()); } private char nc() { return (char)skip(); } private String ns() { int b = skip(); StringBuilder sb = new StringBuilder(); while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ') sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } private char[] ns(int n) { char[] buf = new char[n]; int b = skip(), p = 0; while(p < n && !(isSpaceChar(b))){ buf[p++] = (char)b; b = readByte(); } return n == p ? buf : Arrays.copyOf(buf, p); } private int[] na(int n) { int[] a = new int[n]; for(int i = 0;i < n;i++)a[i] = ni(); return a; } private long[] nal(int n) { long[] a = new long[n]; for(int i = 0;i < n;i++)a[i] = nl(); return a; } private char[][] nm(int n, int m) { char[][] map = new char[n][]; for(int i = 0;i < n;i++)map[i] = ns(m); return map; } private int[][] nmi(int n, int m) { int[][] map = new int[n][]; for(int i = 0;i < n;i++)map[i] = na(m); return map; } private int ni() { return (int)nl(); } private long nl() { long num = 0; int b; boolean minus = false; while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')); if(b == '-'){ minus = true; b = readByte(); } while(true){ if(b >= '0' && b <= '9'){ num = num * 10 + (b - '0'); }else{ return minus ? -num : num; } b = readByte(); } } private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); } }