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.awt.Point;
import java.io.*;
import java.math.BigInteger;
import java.util.*;

import static java.lang.Math.*;

public class B implements Runnable{
	
	final boolean ONLINE_JUDGE = System.getProperty("ONLINE_JUDGE")!=null;
	BufferedReader in;
	PrintWriter out;
	StringTokenizer tok = new StringTokenizer("");
	
	void init() throws FileNotFoundException{
		if (ONLINE_JUDGE){
			in = new BufferedReader(new InputStreamReader(System.in));
			out = new PrintWriter(System.out);
		}else{
			in = new BufferedReader(new FileReader("input.txt"));
			out = new PrintWriter("output.txt");
		}
	}
	
	String readString() throws IOException{
		while(!tok.hasMoreTokens()){
			tok = new StringTokenizer(in.readLine());
		}
		return tok.nextToken();
	}
	
	int readInt() throws IOException{
		return Integer.parseInt(readString());
	}
	
	long readLong() throws IOException{
		return Long.parseLong(readString());
	}
	
	double readDouble() throws IOException{
		return Double.parseDouble(readString());
	}
	
	public static void main(String[] args){
		new Thread(null, new B(), "", 256 * (1L << 20)).start();
	}
	
	public void run(){
		try{
			long t1 = System.currentTimeMillis();
			init();
			solve();
			out.close();
			long t2 = System.currentTimeMillis();
			System.err.println("Time = "+(t2-t1));
		}catch (Exception e){
			e.printStackTrace(System.err);
			System.exit(-1);
		}
	}
	
	void solve() throws IOException{
		int n = readInt();
		int[] count = new int[101];
		for (int i = 0; i < n; i++){
			count[readInt()]++;
		}
		long res = 0;
		for (int i = 0; i < 101; i++){
			res += count[i] / 2;
		}
		out.print(res / 2);
	}
	
	static public class Utils {
		
		private Utils() {}
		
		public static void swap(int x, int y){
			x ^= y;
			y ^= x;
			x ^= y;
		}

		public static long mergeSort(int[] a) { // ���������� ���-�� �������� � �������� �������
			return mergeSort(a, 0, a.length - 1);
		}

		private static long mergeSort(int[] a, int leftIndex, int rightIndex) {
			final int MAGIC_VALUE = 50;
			if (leftIndex < rightIndex) {
				if (rightIndex - leftIndex <= MAGIC_VALUE) {
					return insertionSort(a, leftIndex, rightIndex);
				} else {
					int middleIndex = (leftIndex + rightIndex) / 2;
					return mergeSort(a, leftIndex, middleIndex) +
					mergeSort(a, middleIndex + 1, rightIndex) +
					merge(a, leftIndex, middleIndex, rightIndex);
				}
			}
			return 0;
		}

		private static long merge(int[] a, int leftIndex, int middleIndex, int rightIndex) {
			int length1 = middleIndex - leftIndex + 1;
			int length2 = rightIndex - middleIndex;
			int[] leftArray = new int[length1+1];
			int[] rightArray = new int[length2+1];
			System.arraycopy(a, leftIndex, leftArray, 0, length1);
			System.arraycopy(a, middleIndex + 1, rightArray, 0, length2);
			leftArray[length1] = rightArray[length2] = Integer.MAX_VALUE;
			long res = 0;
			for (int k = leftIndex, i = 0, j = 0; k <= rightIndex; k++) {
				if (leftArray[i] > rightArray[j]){
					a[k] = rightArray[j++];
					res += length1 - i;
				}else a[k] = leftArray[i++];
			}
			return res;
		}

		private static long insertionSort(int[] a, int leftIndex, int rightIndex) {
			long res = 0;
			for (int i = leftIndex + 1; i <= rightIndex; i++) {
				int current = a[i];
				int j = i - 1;
				while (j >= leftIndex && a[j] > current) {
					a[j + 1] = a[j];
					j--;
					res++;
				}
				a[j + 1] = current;
			}
			return res;
		}
		
		public static int median(int[] a){
			return select(a, 0, a.length - 1, a.length / 2 - 1);
		}
		
		public static int select(int[] a, int i){
			return select(a, 0, a.length - 1, i);
		}
		
		private static int select(int[] a, int l, int r, int i){
			if (l == r) return a[l];
			int len = (r - l) / 5 + 1;
			int[] x = new int[len];
			for (int j = 0; j < len; j++){
				int leftIndex = l + j * 5;
				int rightIndex = min(leftIndex + 4, r);
				insertionSort(a, leftIndex, rightIndex);
				x[j] = a[(rightIndex+leftIndex)/2];
			}
			int med = median(x);
			int m = partition(a, l, r, med);
			int k = m - l;
			if (i == k) return a[k+l];
			else return i < k? select(a, l, m - 1, i): select(a, m + 1, r, i - k - 1);
		}
		
		private static int partition(int[] a, int l, int r, int med){
			int i = l;
			for (int j = l; j <= r; j++){
				if (a[j] < med){
					swap(a[i++], a[j]);
				}
			}
			return i;
		}
		
		public static int median(int[] x, int[] y){
			return median(x, 0, x.length - 1, y, 0, y.length - 1);
		}
		
		private static int median(int[] x, int xl, int xr, int[] y, int yl, int yr){ // ����� ������� ���� ��������������� �������� ���������� �����
			if (xl == xr){
				int ind = xl + yl;
				for (; ind < x.length - 1 && yl < yr; yl++, ind++);
				return ind == x.length - 1? min(x[xl], y[yl]): max(x[xl], y[yl]);
			}
			if (yl == yr){
				int ind = xl + yl;
				for (; ind < y.length - 1 && xl < xr; xl++, ind++);
				return ind == y.length - 1? min(x[xl], y[yl]): max(x[xl], y[yl]);
			}
			int mdx = (xl + xr) / 2;
			int mdy = (yl + yr) / 2;
			return x[mdx] < y[mdy]? median(x, mdx, xr, y, yl, mdy): median(x, xl, mdx, y, mdy, yr);
		}
		
		public static final int[][] step8 = {{-1, 0}, {1, 0}, {0, -1}, {0, 1},
									{-1, -1}, {1, -1}, {-1, 1}, {1, 1}};

		public static final int[][] stepKnight = {{-2, -1}, {-2, 1}, {-1, -2}, {-1, 2},
											{1, -2}, {1, 2}, {2, -1}, {2, 1}};
		
		public static long gcd(long a, long b){
			if (a == 0)	return b;
			return gcd(b % a, a);
		}
		
		public static long lcm(long a, long b){
			return a / gcd(a, b)*b;
		}

		public static long[] gcdPlus(long a, long b){
			long[] d = new long[3];
			if (a == 0){
				d[0] = b;
				d[1] = 0;
				d[2] = 1;
			}else{
				d = gcdPlus(b % a, a);
				long r = d[1];
				d[1] = d[2] - b/a*d[1];
				d[2] = r;
			}
			return d;
		}
		
		public static long binpow(long a, int n){
			if (n == 0)	return 1;
			if ((n & 1) == 0){
				long b = binpow(a, n/2);
				return b*b;
			}else return binpow(a, n - 1)*a;
		}
		
		public static long binpowmod(long a, int n, long m){
			if (m == 1) return 0;
			if (n == 0)	return 1;
			if ((n & 1) == 0){
				long b = binpowmod(a, n/2, m);
				return (b*b) % m;
			}else return binpowmod(a, n - 1, m)*a % m;
		}
		
		public static long f(long n, int x, int k){ //���-�� ���������� ����� (������� 0), ���������� � ���� ����� �� 0 �� k-1
			if (n == 0)	return 1;
			long b = binpow(10, x - 1);
			long c = n / b;
			return (c < k? c: k)*binpow(k, x - 1) + (c < k? 1: 0)*f(n % b, x - 1, k);
		}
		
		public static long fib(int n){
			if (n == 0) return 0;
			if ((n & 1) == 0){
				long f1 = fib(n/2 - 1);
				long f2 = fib(n/2 + 1);
				return f2*f2 - f1*f1;
			}else{
				long f1 = fib(n/2);
				long f2 = fib(n/2 + 1);
				return f1*f1 + f2*f2;
			}
		}
		
		public static BigInteger BigFib(int n){
			if (n == 0) return BigInteger.ZERO;
			if ((n & 1) == 0){
				BigInteger f1 = BigFib(n/2 - 1);
				f1 = f1.multiply(f1);
				BigInteger f2 = BigFib(n/2 + 1);
				f2 = f2.multiply(f2);
				return f2.subtract(f1);
			}else{
				BigInteger f1 = BigFib(n/2);
				f1 = f1.multiply(f1);
				BigInteger f2 = BigFib(n/2 + 1);
				f2 = f2.multiply(f2);
				return f2.add(f1);
			}
		}
		
		public static long phi(long n){
			int[] p = new int[1];
			Sieve(p, (int)ceil(sqrt(n)) + 2);
			long phi = 1;
			for (int i = 0; i < p.length; i++){
				long x = 1;
				while (n % p[i] == 0){
					n /= p[i];
					x *= p[i];
				}
				phi *= x - x/p[i];
			}
			if (n != 1) phi *= n - 1;
			return phi;
		}
		
		public static boolean IsProbablyPrimeSqrt(long n){
			if (n == 1)	return false;
			if ((n & 1) == 0) return (n == 2);
			for (int j = 3; j < sqrt(n) + 1; j += 2){
				if (n % j == 0)	return false;
			}
			return true;
		}

		public static void Sieve(int[] p, int n){
			boolean[] b = new boolean[n+1];
			Arrays.fill(b, true);
			b[0] = false;
			b[1] = false;
			long nLong = n;
			int j=0;
			for (int i = 1; i <= n; i++) {
				if (b[i]){
					j++;
					if (((long)i)*i <= nLong) {
						for (int k = i*i; k <= n; k += i) {
							b[k] = false;
						}
					}
				}
			}
			p = new int[j];
			Arrays.fill(p, 0);
			j=0;
			for (int i = 2; i <= n; i++) {
				if (b[i]){
					p[j]=i;
					j++;
				}
			}
		}
		
		public static class PointD{
			
			double x, y;
			
			public PointD(double x, double y){
				this.x = x;
				this.y = y;
			}
			
			public double d(PointD p){
				return sqrt(d2(p));
			}
			
			public double d2(PointD p){
				return (x - p.x) * (x - p.x) + (y - p.y) * (y - p.y); 
			}
		}
		
		public static class Point3D{
			
			double x, y, z;
			
			public Point3D(double x, double y, double z){
				this.x = x;
				this.y = y;
				this.z = z;
			}
			
			public double d(Point3D p){
				return sqrt(d2(p));
			}
			
			public double d2(Point3D p){
				return (x - p.x) * (x - p.x) + (y - p.y) * (y - p.y) + (z - p.z) * (z - p.z); 
			}
		}
		
		public static int[][] Palindromes(String s){ // ���-�� ���� �������� - ����������� � ������
			char[] c = s.toCharArray();
			int n = c.length;
			int[][] d = new int[2][n];
			int l = 0, r = -1;
			for (int i = 0; i < n; i++){
				int j = (i > r? 0: min(d[0][l+r-i+1], r-i+1)) + 1;
				for (; i - j >= 0 && i + j - 1< n && c[i-j] == c[i+j-1]; j++);
				d[0][i] = --j;
				if (i + d[0][i] - 1 > r){
					r = i + d[0][i] - 1;
					l = i - d[0][i];
				}
			}
			l = 0;
			r = -1;
			for (int i = 0; i < n; i++){
				int j = (i > r? 0: min(d[1][l+r-i], r-i)) + 1;
				for (; i - j >= 0 && i + j < n && c[i-j] == c[i+j]; j++);
				d[1][i] = --j;
				if (i + d[1][i] > r){
					r = i + d[1][i];
					l = i - d[1][i];
				}
			}
			return d;
		}
		
		public static class Permutation {
			
			private int[] a;
			private int n;
			
			public Permutation(int n){
				this.n = n;
				a = new int[n];
				for (int i = 0; i < n; i++){
					a[i] = i;
				}
			}
			
			public boolean nextPermutation(){ //������� � do{}while(nextPermutation(a));
				int i = n - 1;
				for (i = n - 2; i >= 0 && a[i] < a[i+1]; i--);
				if (i == -1) return false;
				int jMin = i + 1;
				for (int j = n - 1; j > i; j--){
					if (a[i] < a[j] && a[j] < a[jMin]){
						jMin = j;
					}
				}
				swap(i, jMin);
				for (int j = 1; j <= (n - i)/2; j++){
					swap(i + j, n - j);
				}
				return true;
			}
			
			
			public int get(int i){
				return a[i];
			}
			
			private void swap(int i, int j){
				a[i] ^= a[j];
				a[j] ^= a[i];
				a[i] ^= a[j];
			}
		}
		
		public static class Fraction implements Comparable<Fraction>, Cloneable{
			
			public final Fraction FRACTION_ZERO = new Fraction();
			public final Fraction FRACTION_ONE = new Fraction(1);
			public long numerator = 0;
			public long denominator = 1;
			
			public Fraction(){
				numerator = 0;
				denominator = 1;
			}
			
			public Fraction(long numerator){
				this.numerator = numerator;
				denominator = 1;
			}
			
			public Fraction(long numerator, long denominator){
				this.numerator = numerator;
				this.denominator = denominator;
				Cancellation();
			}
			
			public Fraction(double numerator, double denominator, int accuracy){
				this.numerator = (long)(numerator*pow(10,accuracy));
				this.denominator = (long)(denominator*pow(10,accuracy));
				Cancellation();
			}
			
			public Fraction(String s){
				if (s.charAt(0) == '-'){
					denominator = -1;
					s = s.substring(1);
				}
				if (s.indexOf("/") != -1){
					denominator *= Integer.parseInt(s.substring(s.indexOf("/") + 1));
				}
				if (s.indexOf(" ") != -1){
					numerator = Integer.parseInt(s.substring(0, s.indexOf(" "))) * abs(denominator) + Integer.parseInt(s.substring(s.indexOf(" ") + 1, s.indexOf("/")));
				}else{
					if (s.indexOf("/") != -1){
						numerator = Integer.parseInt(s.substring(0, s.indexOf("/")));
					}else{
						numerator = Integer.parseInt(s)*abs(denominator);
					}
				}
				this.Cancellation();
			}
			
			private void Cancellation(){
				long g = gcd(abs(numerator), abs(denominator));
				numerator /= g;
				denominator /= g;
				if (denominator < 0){
					numerator *= -1;
					denominator *= -1;
				}
			}
			
			public String toString(){
				String s = "";
				if (numerator == 0){
					return "0";
				}
				if (numerator < 0){
					s += "-";
				}
				if (abs(numerator) >= denominator){
					s += Long.toString(abs(numerator) / denominator) + " ";
				}
				if (abs(numerator) % denominator != 0){
					s += Long.toString(abs(numerator) % denominator);
				}else{
					s = s.substring(0, s.length()-1);
				}
				if (denominator != 1){
					s += "/" + Long.toString(denominator);
				}
				return s;
			}
			
			public Fraction add(Fraction f){
				Fraction fResult = new Fraction();
				fResult.denominator = lcm(denominator, f.denominator);
				fResult.numerator = numerator * fResult.denominator / denominator + f.numerator * fResult.denominator / f.denominator;
				fResult.Cancellation();
				return fResult;
			}
			
			public Fraction subtract(Fraction f){
				Fraction fResult = new Fraction();
				fResult.denominator = lcm(denominator, f.denominator);
				fResult.numerator = numerator * fResult.denominator / denominator - f.numerator * fResult.denominator / f.denominator;
				fResult.Cancellation();
				return fResult;
			}
			
			public Fraction multiply(Fraction f){
				Fraction fResult = new Fraction();
				fResult.numerator = numerator * f.numerator;
				fResult.denominator = denominator * f.denominator;
				fResult.Cancellation();
				return fResult;
			}
			
			public Fraction divide(Fraction f){
				Fraction fResult = new Fraction();
				fResult.numerator = numerator * f.denominator;
				fResult.denominator = denominator * f.numerator;
				fResult.Cancellation();
				return fResult;
			}
			
			@Override
			public int compareTo(Fraction f){
				long g = gcd(denominator, f.denominator);
				long res = numerator * (f.denominator / g) - f.numerator * (denominator / g);
				if (res < 0){
					return -1;
				}
				if (res > 0){
					return 1;
				}
				return 0;
			}
			
			public Fraction clone(){
				Fraction fResult = new Fraction(numerator, denominator);
				return fResult;
			}
			
			public Fraction floor(){
				Fraction fResult = this.clone();
				fResult.numerator = (fResult.numerator / fResult.denominator) * fResult.denominator;
				return fResult;
			}
			
			public Fraction ceil(){
				Fraction fResult = this.clone();
				fResult.numerator = (fResult.numerator/fResult.denominator + 1) * fResult.denominator;
				return fResult;
			}
			
			public Fraction binpow(int n){
				if (n==0) return FRACTION_ONE;
				if ((n&1)==0){
					Fraction f=this.binpow(n/2);
					return f.multiply(f);
				}else return binpow(n-1).multiply(this);
			}
		}
		
		public static class FenwickTree_1{	//One-dimensional array
			
			private int n;
			private long[] a;
			private long[] tree;
			
			public FenwickTree_1(int n){
				this.n = n;
				tree = new long[n];
				a = new long[n];
			}
			
			public long sum(int xl, int xr){
				return sum(xr) - sum(xl);
			}
			
			private long sum(int x){
				long result = 0;
				for (int i = x; i >= 0; i = (i & (i + 1)) - 1){
					result += tree[i];
				}
				return result;
			}
			
			public void update(int x, long new_value){
				long delta = new_value - a[x];
				a[x] = new_value;
				for (int i = x; i < n; i = (i | (i + 1))){
					tree[i] += delta;
				}
			}
		}
		
		public static class FenwickTree_2{	//Two-dimensional array
			
			private int n, m;
			private long[][] a;
			private long[][] tree;
			
			public FenwickTree_2(int n, int m){
				this.n = n;
				this.m = m;
				tree = new long[n][m];
				a = new long[n][m];
			}
			
			public long sum(int xl, int yl, int xr, int yr){
				return sum(xr, yr) - sum(xl - 1, yr) - sum(xr, yl - 1) + sum(xl - 1, yl - 1);
			}
			
			private long sum(int x, int y){
				long result = 0;
				for (int i = x; i >= 0; i = (i & (i + 1)) - 1){
					for (int j = y; j >= 0; j = (j & (j + 1)) - 1){
						result+=tree[i][j];
					}
				}
				return result;
			}
			
			public void update(int x, int y, long new_value){
				long delta = new_value - a[x][y];
				a[x][y] = new_value;
				for (int i = x; i < n; i = (i | (i + 1))){
					for (int j = y; j < m; j = (j | (j + 1))){
						tree[i][j] += delta;
					}
				}
			}
		}
		
		public static class FenwickTree_3{	//Three-dimensional array
			
			private int n, m, l;
			private long[][][] a;
			private long[][][] tree;
			
			public FenwickTree_3(int n, int m, int l){
				this.n = n;
				this.m = m;
				this.l = l;
				tree = new long[n][m][l];
				a = new long[n][m][l];
			}
			
			public long sum(int xl, int yl, int zl, int xr, int yr, int zr){
				return sum(xr, yr, zr) - sum(xl - 1, yr, zr)
				+ sum(xl - 1, yr, zl - 1) - sum(xr, yr, zl - 1)
				- sum(xr, yl - 1, zr) + sum(xl - 1, yl - 1, zr)
				- sum(xl - 1, yl - 1, zl - 1) + sum(xr, yl - 1, zl - 1);
			}
			
			private long sum(int x, int y, int z){
				long result = 0;
				for (int i = x; i >= 0; i = (i & (i + 1)) - 1){
					for (int j = y; j >= 0; j = (j & (j + 1)) - 1){
						for (int k = z; k >= 0; k = (k & (k + 1)) - 1){
							result += tree[i][j][k];
						}
					}
				}
				return result;
			}
			
			public void update(int x, int y, int z, long new_value){
				long delta = new_value - a[x][y][z];
				a[x][y][z] = new_value;
				for (int i = x; i < n; i = (i | (i + 1))){
					for (int j = y; j < m; j = (j | (j + 1))){
						for (int k = z; k < l; k = (k | (k + 1))){
							tree[i][j][k] += delta;
						}
					}
				}
			}
		}
		
		static public class YoungTable{
			
			private long[] table;
			private int n;
			private int countOfElements;
			
			public YoungTable(int nmax) {
				n = (int) floor(sqrt(nmax)) + 1;
				table = new long[n*n];
				Arrays.fill(table, Long.MAX_VALUE);
				countOfElements = 0;
			}
			
			public YoungTable(long[] a){
				n = (int) floor(sqrt(a.length)) + 1;
				table = new long[n*n];
				Arrays.fill(table, Long.MAX_VALUE);
				countOfElements = 0;
				for (int i = 0; i < a.length; i++){
					put(a[i]);
				}
			}
			
			int size(){
				return countOfElements;
			}
			
			void put(long v) throws ArrayIndexOutOfBoundsException{
				if (countOfElements == table.length) throw new ArrayIndexOutOfBoundsException();
				table[countOfElements] = v;
				YoungTablefyUp(countOfElements++);
			}
			
			private void YoungTablefyUp(int ind){
				int maxInd = ind;
				if (ind >= n && table[maxInd] < table[ind-n]) maxInd = ind - n;
				if (ind % n > 0 && table[maxInd] < table[ind-1]) maxInd = ind - 1;
				if (maxInd != ind){
					swap(maxInd, ind);
					YoungTablefyUp(maxInd);
				}
			}
			
			private void swap(int i, int j){
				table[i] ^= table[j];
				table[j] ^= table[i];
				table[i] ^= table[j];
			}
			
			boolean contains(long v){
				int i = n - 1;
				int j = 0;
				int ind = i * n + j;
				boolean exit = true;
				do{
					exit = true;
					while (i > 0 && table[ind] > v){
						i--;
						ind -= n;
						exit = false;
					}
					while (j < n - 1 && table[ind] < v){
						j++;
						ind++;
						exit = false;
					}
				}while (!exit);
				return table[ind] == v;
			}
			
			long peek() throws ArrayIndexOutOfBoundsException{
				if (countOfElements == 0) throw new ArrayIndexOutOfBoundsException();
				return table[0];
			}
			
			long poll() throws ArrayIndexOutOfBoundsException{
				if (countOfElements == 0) throw new ArrayIndexOutOfBoundsException();
				long res = table[0];
				table[0] = table[--countOfElements];
				table[countOfElements] = Long.MAX_VALUE;
				YoungTablefyDown(0);
				return res;
			}
			
			private void YoungTablefyDown(int ind){
				int minInd = ind;
				if (ind % n < n - 1 && table[minInd] > table[ind+1]) minInd = ind + 1;
				if (ind / n < n - 1 && table[minInd] > table[ind+n]) minInd = ind + n;
				if (minInd != ind){
					swap(minInd, ind);
					YoungTablefyDown(minInd);
				}
			}
			
			void sort(long[] a){
				YoungTable yt = new YoungTable(a);
				for (int i = 0; i < a.length; i++){
					a[i] = yt.poll();
				}
			}
		}
	}
}

