Problem: Misha hacked the Codeforces site. Then he decided to let all the users change their handles. A user can now change his handle any number of times. But each new handle must not be equal to any handle that is already used or that was used at some point.

Misha has a list of handle change requests. After completing the requests he wants to understand the relation between the original and the new handles of the users. Help him to do that.

Input

The first line contains integer q (1 ≤ q ≤ 1000), the number of handle change requests.

Next q lines contain the descriptions of the requests, one per line.

Each query consists of two non-empty strings old and new, separated by a space. The strings consist of lowercase and uppercase Latin letters and digits. Strings old and new are distinct. The lengths of the strings do not exceed 20.

The requests are given chronologically. In other words, by the moment of a query there is a single person with handle old, and handle new is not used and has not been used by anyone.

Output

In the first line output the integer n — the number of users that changed their handles at least once.

In the next n lines print the mapping between the old and the new handles of the users. Each of them must contain two strings, old and new, separated by a space, meaning that before the user had handle old, and after all the requests are completed, his handle is new. You may output lines in any order.

Each user who changes the handle must occur exactly once in this description.

Examples

Input

5
Misha ILoveCodeforces
Vasya Petrov
Petrov VasyaPetrov123
ILoveCodeforces MikeMirzayanov
Petya Ivanov


Output

3
Petya Ivanov
Misha MikeMirzayanov
Vasya VasyaPetrov123

Solution (in JAVA):

Solution:


        import java.io.*;
     
        import java.math.BigInteger;
        import java.util.*;
     
        public class Graph1 {
        	//static int flag=1;
        	
        	//private static int n,l,r,z,way=0;
    		  private static InputStream stream;
        	private static byte[] buf=new byte[1024];
        	private static int curChar;
        	private static int numChars;
        	private static SpaceCharFilter filter;
        	private static PrintWriter pw;
        	private static long count=0;
            public static void main(String args[] ) throws Exception 
            {
            	InputReader(System.in);
        		pw=new PrintWriter(System.out);
        		soln();
        		pw.close();
            }
     
     
        
    public static boolean PointInTriangle(int p1, int p2, int p3, int p4, int p5, int p6, int p7, int p8)
    {
    int s = p2 * p5 - p1 * p6 + (p6 - p2) * p7 + (p1 - p5) * p8;
    int t = p1 * p4 - p2 * p3 + (p2 - p4) * p7 + (p3 - p1) * p8;
     
    if ((s < 0) != (t < 0))
    return false;
     
    int A = -p4 * p5 + p2 * (p5 - p3) + p1 * (p4 - p6) + p3 * p6;
    if (A < 0.0)
    {
    s = -s;
    t = -t;
    A = -A;
    }
    return s > 0 && t > 0 && (s + t) <= A;
    }
     
      public static float area(int x1, int y1, int x2, int y2, int x3, int y3){
    	  return (float)Math.abs((x1*(y2-y3) + x2*(y3-y1)+ x3*(y1-y2))/2.0);
      }
      public static boolean isPrime(int n)
      {
          // Corner cases
          if (n <= 1)  return false;
          if (n <= 3)  return true;
       
          // This is checked so that we can skip 
          // middle five numbers in below loop
          if (n%2 == 0 || n%3 == 0) return false;
       
          for (int i=5; i*i<=n; i=i+6)
              if (n%i == 0 || n%(i+2) == 0)
                 return false;
       
          return true;
      }
     
     
    //merge Sort
            
            public static void Merge_sort(int a[]){
            	int len=a.length;
            	if(len <2)
            		return ;
            	int mid=len/2;
            	int l[]=new int[mid];
            	int r[] =new int[len-mid];
            	for(int i=0;i<mid;i++)
            		l[i]=a[i];
            	for(int i=mid;i<len;i++)
            		r[i-mid]=a[i];
            	
            	Merge_sort(l);
            	Merge_sort(r);
            	Merge(l,r,a);
            }
            	
            public static void Merge(int []l,int[]r,int a[]){
            	int nl=l.length;
            	int nr=r.length;
            	int i=0,j=0,k=0;
            	
            	while(i <nl && j<nr){
            		if(l[i] > r[j]){
            			a[k]=l[i];
            			k++;
            			i++;
            		}
            		else{
            			a[k]=r[j];
            			k++;
            			j++;
            		}
            		
            		while(i<nl){
            			a[k]=l[i];
            			k++;
            			i++;
            		}
            		while(j<nr){
            			a[k]=r[j];
            			k++;
            			j++;
            		}
            	}
            }
      
        	
        public static boolean isSubSequence(String large,String small,int largeLen,int smallLen){
        //base cases
        	if(largeLen==0)
        		return false;
        	if(smallLen==0)
        		return true;
        	  // If last characters of two strings are matching
        	if(large.charAt(largeLen-1)==small.charAt(smallLen-1))
        		isSubSequence(large, small, largeLen-1, smallLen-1);
        	// If last characters are not matching
        	return isSubSequence(large, small, largeLen-1, smallLen);
        }
     
        // To Get Input
         	// Some Buffer Methods
         
         	public static void InputReader(InputStream stream1) {
         		stream = stream1;
         	}
         
         	private static boolean isWhitespace(int c) {
         		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
         	}
         
         	private static boolean isEndOfLine(int c) {
         		return c == '\n' || c == '\r' || c == -1;
         	}
         
         	private static 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++];
         	}
         
         	private static int nextInt() {
         		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;
         	}
          
         	private static long nextLong() {
         		int c = read();
         		while (isSpaceChar(c))
         			c = read();
         		int sgn = 1;
         		if (c == '-') {
         			sgn = -1;
         			c = read();
         		}
         		long res = 0;
         		do {
         			if (c < '0' || c > '9')
         				throw new InputMismatchException();
         			res *= 10;
         			res += c - '0';
         			c = read();
         		} while (!isSpaceChar(c));
         		return res * sgn;
         	}
          
         	private static String nextToken() {
         		int c = read();
         		while (isSpaceChar(c))
         			c = read();
         		StringBuilder res = new StringBuilder();
         		do {
         			res.appendCodePoint(c);
         			c = read();
         		} while (!isSpaceChar(c));
         		return res.toString();
         	}
          
         	private static String nextLine() {
         		int c = read();
         		while (isSpaceChar(c))
         			c = read();
         		StringBuilder res = new StringBuilder();
         		do {
         			res.appendCodePoint(c);
         			c = read();
         		} while (!isEndOfLine(c));
         		return res.toString();
         	}
         
         	private static int[] nextIntArray(int n) {
         		int[] arr = new int[n];
         		for (int i = 0; i < n; i++) {
         			arr[i] = nextInt();
         		}
         		return arr;
         	}
         	  
         	private static long[] nextLongArray(int n) {
         		long[] arr = new long[n];
         		for (int i = 0; i < n; i++) {
         			arr[i] = nextLong();
         		}
         		return arr;
         	}
         
         	private static void pArray(int[] arr){
         		for (int i=0; i<arr.length; i++) {
         			System.out.print(arr[i] + " ");
         		}
         		System.out.println();
         		return;
         	}
         
         	private static void pArray(long[] arr){
         		for (int i=0; i<arr.length; i++) {
         			System.out.print(arr[i] + " ");
         		}
         		System.out.println();
         		return;		
         	}
         	
         	private static void pArray(boolean[] arr){
         		for (int i=0; i<arr.length; i++) {
         			System.out.print(arr[i] + " ");
         		}
         		System.out.println();
         		return;
         	}
     
         
         	private static boolean isSpaceChar(int c) {
         		if (filter != null)
         			return filter.isSpaceChar(c);
         		return isWhitespace(c);
         	}
          
         	private interface SpaceCharFilter {
         		public boolean isSpaceChar(int ch);
         	}
         
            
         	 private static void soln() {
         
         		 int n=nextInt();
         		 String s[]=new String[n];
         		 for(int i=0;i<n;i++)
         			 s[i]=nextLine();
         		 HashSet hs=new HashSet();
         		 HashMap<String,String> hm=new HashMap<>();
         		 for(int i=0;i<n;i++){
         			 StringTokenizer str=new StringTokenizer(s[i]);
         			 String t=str.nextToken().toString();
         			 if(!hs.contains(t)){
         			 hs.add(t);
         			 String t1=str.nextToken().toString();
         			 for(int j=i+1;j<n;j++){
         				StringTokenizer ss=new StringTokenizer(s[j]);
         				String i1=ss.nextToken().toString();
         				String i2=ss.nextToken().toString();
         				 if(i1.equals(t1)){
         					 hs.add(t1);
         					 //StringTokenizer sr=new StringTokenizer(s[j]);
         						//	 hs.add(sr.nextToken().toString());
         					 t1=i2;
         					 hs.add(t1);
         				 }
         			 }
         			 hm.put(t, t1);
         			 //System.out.println(t+" "+t1);
         		 }
         		 }
         		 System.out.println(hm.size());
         		 Set setOfKeys = hm.keySet();
         		 Iterator it=setOfKeys.iterator();
         		 while(it.hasNext()){
         			 String k=it.next().toString();
         			 System.out.println(k+" "+hm.get(k));
         		 }
         	 }
         	 }
        
        
        class Dsu{
        	private int rank[], parent[] ,n;
        	
        	Dsu(int size){
        		this.n=size+1;
        		rank=new int[n];
        		parent=new int[n];
        	makeSet();
        	}
        	
        	void makeSet(){
        		for(int i=0;i<n;i++){
        			parent[i]=i;
        		}
        	}
        	
        	int find(int x){
        		if(parent[x]!=x){
        			
        			parent[x]=find(parent[x]);
        		}
        		return parent[x];
        	}	
        	
        	void union(int x,int y){
        		int xRoot=find(x);
        		int yRoot=find(y);
        		
        		if(xRoot==yRoot)
        			return;
        		if(rank[xRoot]<rank[yRoot]){
        		parent[xRoot]=yRoot;	
        		}else if(rank[yRoot]<rank[xRoot]){
        			parent[yRoot]=xRoot;
        		}else{
        			parent[yRoot]=xRoot;
        			rank[xRoot]++;
        		}
        		
        	}
        }
        class Graph{
        	private long conse=0,co=0,mac_cons_cat=0;
        	private int V,flag=1;
        	private Stack <Integer>st=new Stack();
        	private LinkedList<Integer > adj[];
        //	boolean Visited[];
        	Graph(int V,int max_cat){
        		V++;
        		
        		this.mac_cons_cat=max_cat;
        		this.V=(V);
        		adj=new LinkedList[V];
        		for(int i=0;i<V;i++)
        			adj[i]=new LinkedList();
        			
        		//Visited=new boolean[V];
        	 
        	}
        	void addEdge(int v,int w){
        		adj[v].add(w);
        	}
        	 public long  dfs(int startVertex,int[] a,boolean[] b){
        		
        		boolean Visited[]=new boolean[V];
        		
        		//flag=1;
        		co=0;
        		conse=0;
        		 if(!Visited[startVertex])  {
        			
        			 //co=1; 
        			 dfsUtil(startVertex,Visited,a,b);
           		 
        		 }
        		 
        		 return co;
        	 }
        	private void dfsUtil(int startVertex, boolean[] Visited,int[] a,boolean[] b) {
        		//System.out.println(pre+" "+startVertex);
        		
        		Visited[startVertex]=true;
        		if(a[startVertex-1]==1)
        			conse++;
        		
        		
        		st.push(startVertex);
        		while(!st.isEmpty()){
        			int top=st.pop();
        			//System.out.println(top);
        			
        			//System.out.println(top);
        		Iterator<Integer> i=adj[top].listIterator();
        	
        		while(i.hasNext()){
        			int n=i.next();
        		//	System.out.println(n+"---");
        			 if( !Visited[n]){
        				Visited[n]=true;
        				if(a[n-1]==1){
        					conse++;
        				}else{
        					if(a[n-1]==1)
        					conse=1;else
        						conse=0;
        				}
        				if(conse>mac_cons_cat)
        					{
        					Iterator<Integer> it=adj[n].listIterator();
        		        	
        					while(it.hasNext()){
        						Visited[it.next()]=true;
        					}
        					//break;
        					}
        					
        				else{
        					if(!b[n]){
                				co++;
                			}
        				
        				}
        				st.push(n);
        				
        				//count++;	
        			
        			
        			
        		}
        		
    			
        	}
        		
        	}
        
        
          
        }
        }