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.io.OutputStreamWriter;
import java.io.BufferedWriter;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.Writer;
import java.util.Collection;
import java.io.IOException;
import java.util.InputMismatchException;
import java.util.NoSuchElementException;
import java.math.BigInteger;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
	public static void main(String[] args) {
		InputStream inputStream = System.in;
		OutputStream outputStream = System.out;
		InputReader in = new InputReader(inputStream);
		OutputWriter out = new OutputWriter(outputStream);
		TaskE solver = new TaskE();
		solver.solve(1, in, out);
		out.close();
	}
}

class TaskE {
    int n;
    EzIntList[] a;
    int[] t;
    int[] f;
    int[] d;
    int[] p;
    boolean[] vis;
    int timer = 0;
    boolean ok = true;

    public void solve(int testNumber, InputReader in, OutputWriter out) {
        n = in.readInt();
        int m = in.readInt();
        a = new EzIntList[n];
        for (int i = 0; i < n; i++) {
            a[i] = new EzIntArrayList();
        }
        for (int i = 0; i < m; i++) {
            int x = in.readInt() - 1;
            int y = in.readInt() - 1;
            a[x].add(y);
            a[y].add(x);
        }
        t = new int[n];
        f = new int[n];
        d = new int[n];
        p = new int[n];
        vis = new boolean[n];
        dfs(0, -1, 0);
        if (!ok) {
            out.printLine(0);
            return;
        }
        for (int x = 0; x < n; x++) {
            for (int i = 0; i < a[x].size(); i++) {
                int y = a[x].get(i);
                if (x < y) {
                    if (y == p[x]) {
                        printEdge(y, x, out);
                    } else if (x == p[y]) {
                        printEdge(x, y, out);
                    } else if (d[x] > d[y]) {
                        printEdge(x, y, out);
                    } else {
                        printEdge(y, x, out);
                    }
                }
            }
        }
    }

    private void printEdge(int x, int y, OutputWriter out) {
        out.printLine((x + 1) + " " + (y + 1));
    }

    private void dfs(int x, int parent, int dist) {
        vis[x] = true;
        t[x] = timer++;
        f[x] = t[x];
        d[x] = dist;
        p[x] = parent;
        for (int i = 0; i < a[x].size(); i++) {
            int y = a[x].get(i);
            if (y != parent) {
                if (vis[y]) {
                    f[x] = Math.min(f[x], t[y]);
                } else {
                    dfs(y, x, dist + 1);
                    f[x] = Math.min(f[x], f[y]);
                    if (f[y] > t[x]) {
                        ok = false;
                    }
                }
            }
        }
    }
}


 interface EzIntList extends EzIntCollection {
    int size();

     EzIntIterator iterator();

     boolean add(int element);

     boolean equals(Object object);

    int hashCode();

    String toString();

    int get(int index);

 }


 class InputReader {

     private InputStream stream;
	private byte[] buf = new byte[1024];
	private int curChar;
	private int numChars;
	private SpaceCharFilter filter;

	public InputReader(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 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 boolean isSpaceChar(int c) {
		if (filter != null)
			return filter.isSpaceChar(c);
		return isWhitespace(c);
	}

	public static boolean isWhitespace(int c) {
		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}

     public interface SpaceCharFilter {
		public boolean isSpaceChar(int ch);
	}
}


 class OutputWriter {
	private final PrintWriter writer;

	public OutputWriter(OutputStream outputStream) {
		writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
	}

	public OutputWriter(Writer writer) {
		this.writer = new PrintWriter(writer);
	}

     public void print(Object...objects) {
		for (int i = 0; i < objects.length; i++) {
			if (i != 0)
				writer.print(' ');
			writer.print(objects[i]);
		}
	}

     public void printLine(Object...objects) {
		print(objects);
		writer.println();
	}

     public void close() {
		writer.close();
	}

     public void printLine(int i) {
		writer.println(i);
	}
}

 class EzIntArrayList implements EzIntList, EzIntStack {
    private static final int DEFAULT_CAPACITY = 10;
    private static final double ENLARGE_SCALE = 2.0;
    private static final int HASHCODE_INITIAL_VALUE = 0x811c9dc5;
    private static final int HASHCODE_MULTIPLIER = 0x01000193;

    private int[] array;
    private int size;

    public EzIntArrayList() {
        this(DEFAULT_CAPACITY);
    }

    public EzIntArrayList(int capacity) {
        if (capacity < 0) {
            throw new IllegalArgumentException("Capacity must be non-negative");
        }
        array = new int[capacity];
        size = 0;
    }

    public EzIntArrayList(EzIntCollection collection) {
        size = collection.size();
        array = new int[size];
        int i = 0;
        for (EzIntIterator iterator = collection.iterator(); iterator.hasNext(); ) {
            array[i++] = iterator.next();
        }
    }

    public EzIntArrayList(int[] srcArray) {
        size = srcArray.length;
        array = new int[size];
        System.arraycopy(srcArray, 0, array, 0, size);
    }

    public EzIntArrayList(Collection<Integer> javaCollection) {
        size = javaCollection.size();
        array = new int[size];
        int i = 0;
        for (int element : javaCollection) {
            array[i++] = element;
        }
    }

    public int size() {
        return size;
    }

     public EzIntIterator iterator() {
        return new EzIntArrayListIterator();
    }

     public boolean add(int element) {
        if (size == array.length) {
            enlarge();
        }
        array[size++] = element;
        return true;
    }

     public int get(int index) {
        if (index < 0 || index >= size) {
            throw new IndexOutOfBoundsException("Index " + index + " is out of range, size = " + size);
        }
        return array[index];
    }

     private void enlarge() {
        int newSize = Math.max(size + 1, (int) (size * ENLARGE_SCALE));
        int[] newArray = new int[newSize];
        System.arraycopy(array, 0, newArray, 0, size);
        array = newArray;
    }

    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        EzIntArrayList that = (EzIntArrayList) o;

        if (size != that.size) {
            return false;
        }
        for (int i = 0; i < size; i++) {
            if (array[i] != that.array[i]) {
                return false;
            }
        }
        return true;
    }

    public int hashCode() {
        int hash = HASHCODE_INITIAL_VALUE;
        for (int i = 0; i < size; i++) {
            hash = (hash ^ PrimitiveHashCalculator.getHash(array[i])) * HASHCODE_MULTIPLIER;
        }
        return hash;
    }

    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append('[');
        for (int i = 0; i < size; i++) {
            sb.append(array[i]);
            if (i < size - 1) {
                sb.append(", ");
            }
        }
        sb.append(']');
        return sb.toString();
    }

    private class EzIntArrayListIterator implements EzIntIterator {
        private int curIndex = 0;

        public boolean hasNext() {
            return curIndex < size;
        }

        public int next() {
            if (curIndex == size) {
                throw new NoSuchElementException("Iterator doesn't have more elements");
            }
            return array[curIndex++];
        }
    }
}


 interface EzIntCollection {
    int size();

     EzIntIterator iterator();

     boolean equals(Object object);

    int hashCode();

    String toString();
}


 interface EzIntIterator {
    boolean hasNext();

    int next();
}


interface EzIntStack extends EzIntCollection {
    int size();

     EzIntIterator iterator();

     boolean equals(Object object);

    int hashCode();

    String toString();

 }

final class PrimitiveHashCalculator {
    private PrimitiveHashCalculator() {
    }

    public static int getHash(int x) {
        return x;
    }

}