Nicholas, a painter is going to paint several new canvases. Nicholas is sure that the canvases will turn out so great that each one will need framing and being hung on the wall. Frames are what Nicholas decided to begin with. 

Nicholas has n sticks whose lengths equal a1, a2, ... an. Nicholas does not want to break the sticks or glue them together. To make a h × w-sized frame, he needs two sticks whose lengths equal h and two sticks whose lengths equal w. Specifically, to make a square frame (when h = w), he needs four sticks of the same length.

Now Nicholas wants to make from the sticks that he has as many frames as possible; to be able to paint as many canvases as possible to fill the frames. Help him in this uneasy task. Note that it is not necessary to use all the sticks Nicholas has.

Input

The first line contains an integer n (1 ≤ n ≤ 100) — the number of sticks. The second line contains n space-separated integers. The i-th integer equals the length of the i-th stick ai (1 ≤ ai ≤ 100).

Output

Print the single number — the maximum number of frames Nicholas can make for his future canvases.

Examples

Input

5
2 4 3 2 3


Output

1

Input

13
2 2 4 4 4 4 6 6 6 7 7 9 9


Output

3

Input

4
3 3 3 5


Output

0
import java.io.*;
import java.util.*;
import java.math.*;

import static java.lang.Math.*;

public class Main implements Runnable {

    StreamTokenizer in;
    BufferedReader reader;
    PrintWriter out;
    StringTokenizer tok;
    Scanner sc;
    boolean timus = System.getProperty("ONLINE_JUDGE")!=null;
    boolean codeforces = true;
    final double eps = 1e-9;
    
    public static void main(String[] args) throws Exception {
        new Thread(new Main()).start();
    }
    
    @Override
    public void run() {
        try {
            if (codeforces) {
                sc = new Scanner(System.in);
                reader = new BufferedReader(new InputStreamReader(System.in));
                in = new StreamTokenizer(reader);
                out= new PrintWriter (new OutputStreamWriter(System.out));
                tok = new StringTokenizer("");
                solve();
                out.flush();
            } else
                if (timus) {
                    sc = new Scanner("input.txt");
                    reader = new BufferedReader(new FileReader("input.txt"));
                    in = new StreamTokenizer(reader);
                    out= new PrintWriter (new FileWriter("output.txt"));
                    tok = new StringTokenizer("");
                    solve();
                    out.flush();
                    out.close();
                } else
                    if (!timus) {
                long begMem = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
                long t1 = System.currentTimeMillis();
                reader = new BufferedReader(new InputStreamReader(System.in));
                in = new StreamTokenizer(reader);
                sc = new Scanner(System.in);
                out= new PrintWriter (new OutputStreamWriter(System.out));
                tok = new StringTokenizer("");
                solve();
                long endMem = Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory();
                out.flush();
                long t2 = System.currentTimeMillis();
                System.out.println("Time:"+(t2-t1));
                System.out.println("Memory:"+(endMem-begMem));
                System.out.println("Total memory: " + (Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory()));
            }
        }
        catch (Exception ex) {
            System.out.println("fail");
            System.exit(1);
        }
    }
    
    public class Chess {
        String coord;
        
        public Chess(String s){
            this.coord=s;
        }
        
        public int toInteger(char s) {
            if (s=='a'||s=='A') return 1;
            else if (s=='b'||s=='B') return 2;
            else if (s=='c'||s=='C') return 3;
            else if (s=='d'||s=='D') return 4;
            else if (s=='e'||s=='E') return 5;
            else if (s=='f'||s=='F') return 6;
            else if (s=='g'||s=='G') return 7;
            else if (s=='h'||s=='H') return 8;
            else return -1;
        }
        
        public String toString(int s) {
            if (s==1) return "a";
            else if (s==2) return "b";
            else if (s==3) return "c";
            else if (s==4) return "d";
            else if (s==5) return "e";
            else if (s==6) return "f";
            else if (s==7) return "g";
            else if (s==8) return "h";
            else return "0";
        }
        
        public pair getPair() {
            String j="";
            j+=coord.charAt(1);
            pair p = new pair(toInteger(coord.charAt(0)),Integer.parseInt(j));
            if (p.x!=-1)
            return p; else
                return new pair(0,0);
        }
        
        public String returnPair(pair p) {
            return toString(p.x)+p.y;
        }
    }
    
    public int nextInt() throws Exception {
        in.nextToken();
        return (int) in.nval;
    }
    
    public String next() throws Exception {
        in.nextToken();
        return in.sval;
    }
    
    public String nextLine() throws Exception {
        return reader.readLine();
    }
    
    public String nextString() throws Exception {
        while (!tok.hasMoreTokens())
            tok = new StringTokenizer(reader.readLine());
        return tok.nextToken();
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(nextString());
    }
    
    public double nextDouble() throws Exception {
        in.nextToken();
        return in.nval;
    }
    
    public class pair {
        int x;
        int y;
        
        public pair(int x, int y) {
            this.x=x;
            this.y=y;
        }
    }
    
    public int gcd(int a, int b) {
        if (a== 0||b==0) return 1;
        if (a<b) {
                int c=b;
                b=a;
                a=c;
        }
        while (a%b!=0) {
                a =a%b;
                if (a<b) {
                        int c=b;
                        b=a;
                        a=c;
                }
        }
        return b;
    }
    
     public int pow(int a, int n) {
         if (n==0) return 1;
         int k=n, b=1, c=a;
         while (k!=0) {
                 if (k%2==0) {
                         k/=2;
                         c*=c;
                 } else {
                         k--;
                         b*=c;
                 }
         }
         return b;
     }
    
    public int lcm(int a, int b) {
        return a*b/gcd(a,b);
    }
    
    public class pairs implements Comparable<pairs> {
        int x;
        int y;
        
        public pairs(int x, int y) {
            this.x=x;
            this.y=y;
        }

        @Override
        public int compareTo(pairs obj) {
            if (this.x<((pairs)obj).x) return 1;
            else if (this.x==(obj).x&&this.y<(obj).y) return 1;
            else if (this.x==(obj).x&&this.y==(obj).y)return 0; else
                return -1;
        }   
    }
    
    public class Graf {
        
        int [][] a;
        int [] colors;
        ArrayList <String> points = new ArrayList<String>();
        LinkedList <Integer> queue = new LinkedList <Integer>();
        boolean [] used;
        boolean cycle;
        int numberOfCycle;
        
        public Graf(int [][]a,String s[]) {
            this.a=new int [s.length][s.length];
            this.a=a;
            this.colors=new int [s.length];
            this.used=new boolean[s.length];
            for (int i=0; i<s.length;i++) {
                this.colors[i]=0;
                this.points.add(s[i]);
            }
            Arrays.fill(this.used, false);
        }
        
        public void bfs(int i) {
            this.queue.add(i);
            while (!this.queue.isEmpty())
            {
                i = this.queue.pop();
                out.print(points.get(i)+" ");
                this.used[i]=true;
                for (int j=0; j<this.points.size();j++) {
                    if (this.a[i][j]==1&&!this.queue.contains(j)&&!this.used[j]) {
                        this.a[i][j]=0;
                        this.a[j][i]=0;
                        this.queue.addLast(j);
                    }
                }
            }
        }
        
        public void dfs(int i) {
            this.colors[i]=1;
            out.print(points.get(i)+" ");
            for (int j=0; j<this.colors.length;j++) {
                if (this.a[i][j]==1&&this.colors[j]==0) {
                    this.colors[j]=1;
                    this.a[i][j]=0;
                    this.a[j][i]=0;
                    dfs(j);
                } else if (this.a[i][j]==1&&this.colors[j]==1) {
                    this.cycle=true;
                    this.numberOfCycle++;
                }
            }
            this.colors[i]=2;
        }   
    }
    
    public class Time {
        
        int h;
        int min;
        int sec;
        
        public Time(String s) {
            String [] st = s.split(":");
            this.h =Integer.parseInt(st[0]);
            this.min =Integer.parseInt(st[1]);
            this.sec =(st[2]!=null)? Integer.parseInt(st[2]):0;
        }
        
        public String toString(int a) {
            String h = Integer.toString(this.h);
            String min = Integer.toString(this.min);
            String sec = Integer.toString(this.sec);
            if (h.length()==1) {
                h='0'+h;
            }
            if (min.length()==1) {
                min='0'+min;
            }
            if (sec.length()==1) {
                sec='0'+sec;
            }
            if (a==5) {
                return h+":"+min;
            } else {
                return h+":"+min+":"+sec;
            }
        }
        
        public void to12HoursFormat () {
            h%=12;
        }
        
        public void add (int  h,int min,int s) {
            this.sec+=s;
            if (this.sec>=60) {
                this.min++;
                this.sec%=60;
            }
            this.min+=min;
            if (this.min>=60) {
                this.h++;
                this.min%=60;
            }
            this.h+=h;
            if (this.h>=24) {
                this.h%=24;
            }
        }
    }
    
    public int[] findPrimes(int x) {
        boolean[] erat = new boolean[x-1];
        List<Integer> t = new ArrayList<Integer>();
        int l=0, j=0;
        for (int i=2;i<x; i++) {
                if (erat[i-2]) continue;
                t.add(i);
                l++;
                j=i*2;
                while (j<x) {
                        erat[j-2]=true;
                        j+=i;
                }
        }
        int[] primes = new int[l];
        Iterator<Integer> iterator = t.iterator();
        for (int i = 0; iterator.hasNext(); i++) {
                primes[i]=iterator.next().intValue();
        }
        return primes;
    }
    
    public double dist(pair a,pair b) {
        return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
    }
    
    public void solve() throws Exception {
        int n = nextInt();
        HashMap <Integer,Integer> hm = new HashMap <Integer,Integer>();
        int ans=0;
        for (int i=0; i<n;i++) {
            int q = nextInt();
            if (hm.containsKey(q)) {
                hm.put(q,hm.get(q)+1);
            } else {
                hm.put(q,1);
            }
        }
        for (Integer q:hm.values()) {
            if (q >=2) {
                ans+=q/2;
            }
        }
        out.println(ans/2);
    }
}
