Problem: Berland has n cities, some of them are connected by bidirectional roads. For each road we know whether it is asphalted or not.

The King of Berland Valera II wants to asphalt all roads of Berland, for that he gathered a group of workers. Every day Valera chooses exactly one city and orders the crew to asphalt all roads that come from the city. The valiant crew fulfilled the King's order in a day, then workers went home.

Unfortunately, not everything is as great as Valera II would like. The main part of the group were gastarbeiters — illegal immigrants who are enthusiastic but not exactly good at understanding orders in Berlandian. Therefore, having received orders to asphalt the roads coming from some of the city, the group asphalted all non-asphalted roads coming from the city, and vice versa, took the asphalt from the roads that had it.

Upon learning of this progress, Valera II was very upset, but since it was too late to change anything, he asked you to make a program that determines whether you can in some way asphalt Berlandian roads in at most n days. Help the king.

Input

The first line contains two space-separated integers n, m <image> — the number of cities and roads in Berland, correspondingly. Next m lines contain the descriptions of roads in Berland: the i-th line contains three space-separated integers ai, bi, ci (1 ≤ ai, bi ≤ n; ai ≠ bi; 0 ≤ ci ≤ 1). The first two integers (ai, bi) are indexes of the cities that are connected by the i-th road, the third integer (ci) equals 1, if the road was initially asphalted, and 0 otherwise. 

Consider the cities in Berland indexed from 1 to n, and the roads indexed from 1 to m. It is guaranteed that between two Berlandian cities there is not more than one road.

Output

In the first line print a single integer x (0 ≤ x ≤ n) — the number of days needed to asphalt all roads. In the second line print x space-separated integers — the indexes of the cities to send the workers to. Print the cities in the order, in which Valera send the workers to asphalt roads. If there are multiple solutions, print any of them. 

If there's no way to asphalt all roads, print "Impossible" (without the quotes).

Examples

Input

4 4
1 2 1
2 4 0
4 3 1
3 2 0


Output

4
3 2 1 3


Input

3 3
1 2 0
2 3 0
3 1 0


Output

Impossible

Solution (in JAVA):

Solution:
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.BitSet;
import java.util.Calendar;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.PriorityQueue;
import java.util.SortedSet;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;

/**
 * #
 * 
 * @author pttrung
 */
public class E_Round_141_Div2 {

	public static long MOD = 1000000007;

	public static void main(String[] args) throws FileNotFoundException {
		// PrintWriter out = new PrintWriter(new FileOutputStream(new File(
		// "output.txt")));
		PrintWriter out = new PrintWriter(System.out);
		Scanner in = new Scanner();
		int n = in.nextInt();
		int m = in.nextInt();
		Edge[]data = new Edge[m];
		ArrayList<Integer>[]map = new ArrayList[n];
		for(int i = 0; i <n; i++){
			map[i] = new ArrayList();
		}
		for(int i = 0; i < m; i++){
			data[i] = new Edge(in.nextInt() - 1, in.nextInt() - 1, in.nextInt());
			map[data[i].x].add(i);
			map[data[i].y].add(i);
		}
		int[]check = new int[n];
		Arrays.fill(check, -1);
		boolean ok = true;
		for(int i = 0; i < n && ok; i++){
			if(check[i] == -1){
				ok &= cal(i, check, map, data);
			}
		}
		if(ok){
			int result = 0;
			StringBuilder builder= new StringBuilder();
			for(int i = 0; i < n ; i++){
				if(check[i] == 1){
					result++;
					builder.append((i + 1) + " ");
				}
			}
			out.println(result);
			out.println(builder.toString());
		}else{
			out.println("Impossible");
		}
		out.close();
	}
	
	static boolean cal(int index,int[]check, ArrayList<Integer>[]map, Edge[]data){
		LinkedList<Integer>q = new LinkedList();
		q.add(index);
		int[]cur = new int[check.length];
		Arrays.fill(cur, -1);
		boolean ok = true;
		cur[index] = 0;
		while(!q.isEmpty() && ok){
			int node = q.pollFirst();
			for(int i : map[node]){
				int nxt = data[i].x == node ? data[i].y : data[i].x;
				if(cur[nxt] == -1){
					if(data[i].cost == 1){
						cur[nxt] = cur[node];
					}else{
						cur[nxt] = 1 - cur[node];
					}
					q.add(nxt);
				}else{
					if(data[i].cost == 1){
						if(cur[nxt] != cur[node]){
							ok = false;
							break;
						}
					}else if(cur[nxt] == cur[node]){
						ok = false;
						break;
					}
				}
			}
		}
		//System.out.println(ok + " " + Arrays.toString(cur));
		if(!ok){
			Arrays.fill(cur, -1);
			cur[index] = 1;
			q = new LinkedList();
			q.add(index);
			while(!q.isEmpty() && ok){
				int node = q.pollFirst();
				for(int i : map[node]){
					int nxt = data[i].x == node ? data[i].y : data[i].x;
					if(cur[nxt] == -1){
						if(data[i].cost == 1){
							cur[nxt] = cur[node];
						}else{
							cur[nxt] = 1 - cur[node];
						}
						q.add(nxt);
					}else{
						if(data[i].cost == 1){
							if(cur[nxt] != cur[node]){
								ok = false;
								break;
							}
						}else if(cur[nxt] == cur[node]){
							ok = false;
							break;
						}
					}
				}
			}
		}
		if(ok){
			for(int i = 0; i < check.length; i++){
				if(cur[i] != -1){
					check[i] = cur[i];
				}
			}
		}
		return ok;
	}

	static class Edge {
		int x, y, cost;

		public Edge(int x, int y, int cost) {
			super();
			this.x = x;
			this.y = y;
			this.cost = cost;
		}
	}

	public static int[] KMP(String val) {
		int i = 0;
		int j = -1;
		int[] result = new int[val.length() + 1];
		result[0] = -1;
		while (i < val.length()) {
			while (j >= 0 && val.charAt(j) != val.charAt(i)) {
				j = result[j];
			}
			j++;
			i++;
			result[i] = j;
		}
		return result;

	}

	public static boolean nextPer(int[] data) {
		int i = data.length - 1;
		while (i > 0 && data[i] < data[i - 1]) {
			i--;
		}
		if (i == 0) {
			return false;
		}
		int j = data.length - 1;
		while (data[j] < data[i - 1]) {
			j--;
		}
		int temp = data[i - 1];
		data[i - 1] = data[j];
		data[j] = temp;
		Arrays.sort(data, i, data.length);
		return true;
	}

	public static int digit(long n) {
		int result = 0;
		while (n > 0) {
			n /= 10;
			result++;
		}
		return result;
	}

	public static double dist(long a, long b, long x, long y) {
		double val = (b - a) * (b - a) + (x - y) * (x - y);
		val = Math.sqrt(val);
		double other = x * x + a * a;
		other = Math.sqrt(other);
		return val + other;

	}

	public static class Point implements Comparable<Point> {

		int x, y;

		public Point(int start, int end) {
			this.x = start;
			this.y = end;
		}

		@Override
		public int hashCode() {
			int hash = 5;
			hash = 47 * hash + this.x;
			hash = 47 * hash + this.y;
			return hash;
		}

		@Override
		public boolean equals(Object obj) {
			if (obj == null) {
				return false;
			}
			if (getClass() != obj.getClass()) {
				return false;
			}
			final Point other = (Point) obj;
			if (this.x != other.x) {
				return false;
			}
			if (this.y != other.y) {
				return false;
			}
			return true;
		}

		@Override
		public int compareTo(Point o) {
			return x - o.x;
		}
	}

	public static class FT {

		long[] data;

		FT(int n) {
			data = new long[n];
		}

		public void update(int index, long value) {
			while (index < data.length) {
				data[index] += value;
				index += (index & (-index));
			}
		}

		public long get(int index) {
			long result = 0;
			while (index > 0) {
				result += data[index];
				index -= (index & (-index));
			}
			return result;

		}
	}

	public static long gcd(long a, long b) {
		if (b == 0) {
			return a;
		}
		return gcd(b, a % b);
	}

	public static long pow(long a, long b) {
		if (b == 0) {
			return 1;
		}
		if (b == 1) {
			return a;
		}
		long val = pow(a, b / 2);
		if (b % 2 == 0) {
			return val * val % MOD;
		} else {
			return val * (val * a % MOD) % MOD;

		}
	}

	static class Scanner {

		BufferedReader br;
		StringTokenizer st;

		public Scanner() throws FileNotFoundException {
			// System.setOut(new PrintStream(new
			// BufferedOutputStream(System.out), true));
			br = new BufferedReader(new InputStreamReader(System.in));
			// br = new BufferedReader(new InputStreamReader(new
			// FileInputStream(new File("input.txt"))));
		}

		public String next() {

			while (st == null || !st.hasMoreTokens()) {
				try {
					st = new StringTokenizer(br.readLine());
				} catch (Exception e) {
					throw new RuntimeException();
				}
			}
			return st.nextToken();
		}

		public long nextLong() {
			return Long.parseLong(next());
		}

		public int nextInt() {
			return Integer.parseInt(next());
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}

		public String nextLine() {
			st = null;
			try {
				return br.readLine();
			} catch (Exception e) {
				throw new RuntimeException();
			}
		}

		public boolean endLine() {
			try {
				String next = br.readLine();
				while (next != null && next.trim().isEmpty()) {
					next = br.readLine();
				}
				if (next == null) {
					return true;
				}
				st = new StringTokenizer(next);
				return st.hasMoreTokens();
			} catch (Exception e) {
				throw new RuntimeException();
			}
		}
	}
}