#include <stdio.h>

void main(void) {
	int n;
	scanf("%d",&n);
	int cardList[n];
	int count = 0;
	for(int i = 0 ; i < n ; i++){
		scanf("%d",&cardList[i]);
		for(int j = 0 ; j < i ; j++ ){
			if(cardList[i] == cardList[j]){
				cardList[i] = 0;
				cardList[j] = 0;
				count++;
				break;
			}
		}
	}
	printf("%d",count);
}