Problem: Bertown has n junctions and m bidirectional roads. We know that one can get from any junction to any other one by the existing roads. 

As there were more and more cars in the city, traffic jams started to pose real problems. To deal with them the government decided to make the traffic one-directional on all the roads, thus easing down the traffic. Your task is to determine whether there is a way to make the traffic one-directional so that there still is the possibility to get from any junction to any other one. If the answer is positive, you should also find one of the possible ways to orient the roads.

Input

The first line contains two space-separated integers n and m (2 ≤ n ≤ 105, n - 1 ≤ m ≤ 3·105) which represent the number of junctions and the roads in the town correspondingly. Then follow m lines, each containing two numbers which describe the roads in the city. Each road is determined by two integers ai and bi (1 ≤ ai, bi ≤ n, ai ≠ bi) — the numbers of junctions it connects.

It is guaranteed that one can get from any junction to any other one along the existing bidirectional roads. Each road connects different junctions, there is no more than one road between each pair of junctions.

Output

If there's no solution, print the single number 0. Otherwise, print m lines each containing two integers pi and qi — each road's orientation. That is the traffic flow will move along a one-directional road from junction pi to junction qi. You can print the roads in any order. If there are several solutions to that problem, print any of them.

Examples

Input

6 8
1 2
2 3
1 3
4 5
4 6
5 6
2 4
3 5


Output

1 2
2 3
3 1
4 5
5 6
6 4
4 2
3 5


Input

6 7
1 2
2 3
1 3
4 5
4 6
5 6
2 4


Output

0

Solution (in JAVA):

Solution:
import java.util.InputMismatchException;
import java.math.BigInteger;
import java.util.Stack;
import java.util.*;
import java.util.Collection;
import java.util.ArrayList;
import java.util.List;
import java.util.Comparator;
import java.io.*;
import java.util.Iterator;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.Arrays;

/**
 * Generated by Contest helper plug-in
 * Actual solution is at the bottom
 */
public class Main {
	public static void main(String[] args) {
		InputReader in = new StreamInputReader(System.in);
		PrintWriter out = new PrintWriter(System.out);
		run(in, out);
	}

	public static void run(InputReader in, PrintWriter out) {
		Solver solver = new TaskE();
		solver.solve(1, in, out);
		Exit.exit(in, out);
	}
}

abstract class InputReader {
	private boolean finished = false;

	public abstract int read();

	public int readInt() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		int sgn = 1;
		if (c == '-') {
			sgn = -1;
			c = read();
		}
		int res = 0;
		do {
			if (c < '0' || c > '9')
				throw new InputMismatchException();
			res *= 10;
			res += c - '0';
			c = read();
		} while (!isSpaceChar(c));
		return res * sgn;
	}

	public String readString() {
		int c = read();
		while (isSpaceChar(c))
			c = read();
		StringBuffer res = new StringBuffer();
		do {
			res.appendCodePoint(c);
			c = read();
		} while (!isSpaceChar(c));
		return res.toString();
	}

	private boolean isSpaceChar(int c) {
		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}

	public void setFinished(boolean finished) {
		this.finished = finished;
	}

	public abstract void close();
}

class StreamInputReader extends InputReader {
	private InputStream stream;
	private byte[] buf = new byte[1024];
	private int curChar, numChars;

	public StreamInputReader(InputStream stream) {
		this.stream = stream;
	}

	public int read() {
		if (numChars == -1)
			throw new InputMismatchException();
		if (curChar >= numChars) {
			curChar = 0;
			try {
				numChars = stream.read(buf);
			} catch (IOException e) {
				throw new InputMismatchException();
			}
			if (numChars <= 0)
				return -1;
		}
		return buf[curChar++];
	}

	public void close() {
		try {
			stream.close();
		} catch (IOException ignored) {
		}
	}
}

class Exit {
	private Exit() {
	}

	public static void exit(InputReader in, PrintWriter out) {
		in.setFinished(true);
		in.close();
		out.close();
	}
}

interface Solver {
	public void solve(int testNumber, InputReader in, PrintWriter out);
}

class GraphUtils {
	public static int[][] buildGraph(int vertexCount, int[] from, int[] to) {
		int edgeCount = from.length;
		int[] degree = new int[vertexCount];
		for (int i = 0; i < edgeCount; i++) {
			degree[from[i]]++;
			degree[to[i]]++;
		}
		int[][] graph = new int[vertexCount][];
		for (int i = 0; i < vertexCount; i++)
			graph[i] = new int[degree[i]];
		for (int i = 0; i < edgeCount; i++) {
			graph[from[i]][--degree[from[i]]] = i;
			graph[to[i]][--degree[to[i]]] = i;
		}
		return graph;
	}

	public static int otherVertex(int vertex, int from, int to) {
		return from + to - vertex;
	}

	public static int[][] buildSimpleGraph(int vertexCount, int[] from, int[] to) {
		int[][] graph = buildGraph(vertexCount, from, to);
		simplifyGraph(from, to, graph);
		return graph;
	}

	private static void simplifyGraph(int[] from, int[] to, int[][] graph) {
		for (int i = 0; i < graph.length; i++) {
			for (int j = 0; j < graph[i].length; j++) {
				graph[i][j] = otherVertex(i, from[graph[i][j]], to[graph[i][j]]);
			}
		}
	}
}

class IOUtils {

	public static void readIntArrays(InputReader in, int[]... arrays) {
		for (int i = 0; i < arrays[0].length; i++) {
			for (int j = 0; j < arrays.length; j++)
				arrays[j][i] = in.readInt();
		}
	}

	}

class TaskE implements Solver {
	private int timer = 0;

	public void solve(int testNumber, InputReader in, PrintWriter out) {
		int vertexCount = in.readInt();
		int edgeCount = in.readInt();
		int[] from = new int[edgeCount];
		int[] to = new int[edgeCount];
		IOUtils.readIntArrays(in, from, to);
		for (int i = 0; i < edgeCount; i++) {
			from[i]--;
			to[i]--;
		}
		int[][] graph = GraphUtils.buildSimpleGraph(vertexCount, from, to);
		boolean[] visited = new boolean[vertexCount];
		int[] fup = new int[vertexCount];
		int[] tin = new int[vertexCount];
		if (dfs(graph, visited, fup, tin, 0, -1)) {
			out.println(0);
			return;
		}
		boolean[] onPath = new boolean[vertexCount];
		Arrays.fill(visited, false);
		dfsPrint(graph, visited, 0, -1, out, onPath);
	}

	private void dfsPrint(int[][] graph, boolean[] visited, int vertex, int previous, PrintWriter out, boolean[] onPath) {
		if (previous != -1 && (!visited[vertex] || onPath[vertex]))
			out.println((previous + 1) + " " + (vertex + 1));
		if (visited[vertex])
			return;
		visited[vertex] = true;
		onPath[vertex] = true;
		for (int i : graph[vertex]) {
			if (i != previous)
				dfsPrint(graph, visited, i, vertex, out, onPath);
		}
		onPath[vertex] = false;
	}

	private boolean dfs(int[][] graph, boolean[] visited, int[] fup, int[] tin, int vertex, int previous) {
		visited[vertex] = true;
		tin[vertex] = fup[vertex] = timer++;
		for (int i : graph[vertex]) {
			if (i == previous)
				continue;
			if (visited[i])
				fup[vertex] = Math.min(fup[vertex], tin[i]);
			else {
				if (dfs(graph, visited, fup, tin, i, vertex))
					return true;
				fup[vertex] = Math.min(fup[vertex], fup[i]);
				if (fup[i] > tin[vertex])
					return true;
			}
		}
		return false;
	}
}