#include<iostream>
#include<string>
#include<string.h>
#include<algorithm>
#include<stdio.h>
#include<cmath>
#include<vector>
#include<utility>
#include<stack>
#include<queue>
#include<list>
#include<bitset>

#define FOR(i, a, b) for(int i=(a);i<=(b);i++)
#define RFOR(i, a, b) for(int i=(a);i>=(b);i--)
#define MOD 1000000007
#define INF 1000000000

using namespace std;


int main(void) {
	int n;
	int a[100001];
	int count = 0;

	cin >> n;
	FOR(i, 0, n-1) {
		cin >> a[i];
	}

	sort(a, a + n);
	FOR(i, 1, n - 1) {
		if (a[i] != a[i - 1]) {
			count++;
			i++;
		}
	}

	cout << count << endl;
	return 0;
}