import java.util.*; @SuppressWarnings("unused") public class Main { private static void solve() { int n = ni(); int[] from = new int[n]; int[] to = new int[n]; int[] w = new int[n]; for (int i = 0; i < n; i++) { from[i] = ni() - 1; to[i] = ni() - 1; w[i] = i; } int[][][] g = packWU(n, from, to, w); int[] ret = dfs(0, -1, g, new boolean[n], new int[n], new int[n], 0); System.gc(); out.println(ret.length); for (int v : ret) { out.print(v + 1 + " "); } out.println(); } private static int[] dfs(int cur, int pre, int[][][] g, boolean[] ved, int[] ehist, int[] vhist, int depth) { ved[cur] = true; vhist[depth] = cur; for (int[] v : g[cur]) { int nex = v[0]; int e = v[1]; ehist[depth] = e; if (nex == pre) continue; if (ved[nex]) { int[] ret = new int[depth + 1]; int p = 0; while (vhist[depth] != nex) { ret[p++] = ehist[depth--]; } ret[p++] = ehist[depth]; return Arrays.copyOf(ret, p); } int[] ret = dfs(nex, cur, g, ved, ehist, vhist, depth + 1); if (ret != null) { return ret; } } return null; } public static int[][][] packWU(int n, int[] from, int[] to, int[] w) { return packWU(n, from, to, w, from.length); } public static int[][][] packWU(int n, int[] from, int[] to, int[] w, int sup) { int[][][] g = new int[n][][]; int[] p = new int[n]; for (int i = 0; i < sup; i++) p[from[i]]++; for (int i = 0; i < sup; i++) p[to[i]]++; for (int i = 0; i < n; i++) g[i] = new int[p[i]][2]; for (int i = 0; i < sup; i++) { --p[from[i]]; g[from[i]][p[from[i]]][0] = to[i]; g[from[i]][p[from[i]]][1] = w[i]; --p[to[i]]; g[to[i]][p[to[i]]][0] = from[i]; g[to[i]][p[to[i]]][1] = w[i]; } return g; } public static void main(String[] args) { new Thread(null, new Runnable() { @Override public void run() { long start = System.currentTimeMillis(); String debug = args.length > 0 ? args[0] : null; if (debug != null) { try { is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug)); } catch (Exception e) { throw new RuntimeException(e); } } reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768); solve(); out.flush(); tr((System.currentTimeMillis() - start) + "ms"); } }, "", 64000000).start(); } private static java.io.InputStream is = System.in; private static java.io.PrintWriter out = new java.io.PrintWriter(System.out); private static java.util.StringTokenizer tokenizer = null; private static java.io.BufferedReader reader; public static String next() { while (tokenizer == null || !tokenizer.hasMoreTokens()) { try { tokenizer = new java.util.StringTokenizer(reader.readLine()); } catch (Exception e) { throw new RuntimeException(e); } } return tokenizer.nextToken(); } private static double nd() { return Double.parseDouble(next()); } private static long nl() { return Long.parseLong(next()); } private static int[] na(int n) { int[] a = new int[n]; for (int i = 0; i < n; i++) a[i] = ni(); return a; } private static char[] ns() { return next().toCharArray(); } private static long[] nal(int n) { long[] a = new long[n]; for (int i = 0; i < n; i++) a[i] = nl(); return a; } private static int[][] ntable(int n, int m) { int[][] table = new int[n][m]; for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { table[i][j] = ni(); } } return table; } private static int[][] nlist(int n, int m) { int[][] table = new int[m][n]; for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { table[j][i] = ni(); } } return table; } private static int ni() { return Integer.parseInt(next()); } private static void tr(Object... o) { if (is != System.in) System.out.println(java.util.Arrays.deepToString(o)); } }