import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.*;
import java.io.File;
import java.io.FileDescriptor;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.io.UncheckedIOException;
import java.lang.reflect.Field;
import java.nio.CharBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.StandardCharsets;

public class Main {
	static final long MOD=1000000007;
	static final long MOD1=998244353;
	static int ans=0;
	public static void main(String[] args){
		PrintWriter out = new PrintWriter(System.out);
		InputReader sc=new InputReader(System.in);
		int N = sc.nextInt();
		int M = sc.nextInt();
		int ans = 0;
		ArrayList<Integer>[] E = new ArrayList[N];
		for (int i = 0; i < E.length; i++) {
			E[i] = new ArrayList<>();
		}
		UnionFindTree uTree = new UnionFindTree(N);
		int[] deg = new int[N];
		for (int i = 0; i < M; i++) {
			int a = sc.nextInt()-1;
			int b = sc.nextInt()-1;
			deg[b]++;
			uTree.union(a, b, 1);
			E[a].add(b);
		}
		ArrayList<Integer>[] group = new ArrayList[N];
		for (int i = 0; i < group.length; i++) {
			group[i] = new ArrayList<>();
		}
		for (int i = 0; i < N; i++) {
			group[uTree.find(i)].add(i);
		}
		ArrayList<String> anStrings = new ArrayList<>();
		for (int i = 0; i < group.length; i++) {
			if(group[i].size()<=1)continue;
			ArrayDeque<Integer> deq = new ArrayDeque<>();
			ArrayList<Integer> topo = new ArrayList<>();
			for (int v: group[i]) {
				if(deg[v]==0)deq.add(v);
			}
			int c = 0;
			while (!deq.isEmpty()) {
				int v = deq.pollFirst();
				topo.add(v);
				c++;
				for (Integer to: E[v]) {
					deg[to]--;
					if (deg[to]==0) {
						deq.add(to);
					}
				}
			}
			for (int j = 0; j < topo.size()-1; j++) {
				anStrings.add((topo.get(j)+1)+" "+(topo.get(j+1)+1));
			}
			if (c==group[i].size()) {
				ans += group[i].size()-1;
			}else {
				ans += group[i].size();
				anStrings.add((topo.get(topo.size()-1)+1)+" "+(topo.get(0)+1));
			}
		}
		out.println(ans);
		for (String string : anStrings) {
			out.println(string);
		}
		out.flush();
  	}
	static class UnionFindTree{
    	int[] par;
    	int[] rank;
    	int[] size;
    	int[] diff_weight;
    	int arraysize;
    	public UnionFindTree(int n) {
    		this.par=new int[n];
    		this.rank=new int[n];
    		this.size=new int[n];
    		this.diff_weight=new int[n];
    		arraysize=n;
    		for (int i = 0; i < arraysize; i++) {
				set(i);
			}
    	}
    	public void set(int i) {
    		par[i]=i;
    		rank[i]=0;
    		size[i]=1;
    		diff_weight[i]=0;
    	}
    	public void union(int x,int y,int w) {
    		w += weight(x); 
    		w -= weight(y);
    		int rootx=find(x);
    		int rooty=find(y);
    		if (rootx==rooty) {
				return;
			}
    		if (rank[rootx]>rank[rooty]) {
				par[rooty]=rootx;
				diff_weight[rooty] = w;
				size[rootx]+=size[rooty];
			}
    		else if (rank[rootx]<rank[rooty]) {
				par[rootx]=rooty;
				w=-w;
				diff_weight[rootx] = w;
				size[rooty]+=size[rootx];
			}
    		else {
    			par[rooty]=rootx;
    			diff_weight[rooty] = w;
    			rank[rootx]++;
				size[rootx]+=size[rooty];
			}
    	}
    	public int find(int x) {
    		if(par[x] == x) return x;
    		int r = find(par[x]);
    		diff_weight[x] += diff_weight[par[x]];
    		return par[x] = r;
    	}
    	public int weight(int x) {
    		find(x);
    		return diff_weight[x];
    	}
    	public int size(int i) {
            return size[find(i)];
        }
    	public int diff(int x, int y) {
    		return weight(y) - weight(x);
    	}
    	public boolean same(int x, int y) {
            return find(x) == find(y);
        }
    }
	static class InputReader { 
		private InputStream in;
		private byte[] buffer = new byte[1024];
		private int curbuf;
		private int lenbuf;
		public InputReader(InputStream in) {
			this.in = in;
			this.curbuf = this.lenbuf = 0;
		}
		public boolean hasNextByte() {
			if (curbuf >= lenbuf) {
				curbuf = 0;
				try {
					lenbuf = in.read(buffer);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (lenbuf <= 0)
					return false;
			}
			return true;
		}
 
		private int readByte() {
			if (hasNextByte())
				return buffer[curbuf++];
			else
				return -1;
		}
 
		private boolean isSpaceChar(int c) {
			return !(c >= 33 && c <= 126);
		}
 
		private void skip() {
			while (hasNextByte() && isSpaceChar(buffer[curbuf]))
				curbuf++;
		}
 
		public boolean hasNext() {
			skip();
			return hasNextByte();
		}
 
		public String next() {
			if (!hasNext())
				throw new NoSuchElementException();
			StringBuilder sb = new StringBuilder();
			int b = readByte();
			while (!isSpaceChar(b)) {
				sb.appendCodePoint(b);
				b = readByte();
			}
			return sb.toString();
		}
 
		public int nextInt() {
			if (!hasNext())
				throw new NoSuchElementException();
			int c = readByte();
			while (isSpaceChar(c))
				c = readByte();
			boolean minus = false;
			if (c == '-') {
				minus = true;
				c = readByte();
			}
			int res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res = res * 10 + c - '0';
				c = readByte();
			} while (!isSpaceChar(c));
			return (minus) ? -res : res;
		}
 
		public long nextLong() {
			if (!hasNext())
				throw new NoSuchElementException();
			int c = readByte();
			while (isSpaceChar(c))
				c = readByte();
			boolean minus = false;
			if (c == '-') {
				minus = true;
				c = readByte();
			}
			long res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res = res * 10 + c - '0';
				c = readByte();
			} while (!isSpaceChar(c));
			return (minus) ? -res : res;
		}
 
		public double nextDouble() {
			return Double.parseDouble(next());
		}
 
		public int[] nextIntArray(int n) {
			int[] a = new int[n];
			for (int i = 0; i < n; i++)
				a[i] = nextInt();
			return a;
		}
		public double[] nextDoubleArray(int n) {
			double[] a = new double[n];
			for (int i = 0; i < n; i++)
				a[i] = nextDouble();
			return a;
		}
		public long[] nextLongArray(int n) {
			long[] a = new long[n];
			for (int i = 0; i < n; i++)
				a[i] = nextLong();
			return a;
		}
 
		public char[][] nextCharMap(int n, int m) {
			char[][] map = new char[n][m];
			for (int i = 0; i < n; i++)
				map[i] = next().toCharArray();
			return map;
		}
	}
}