#include <stdio.h>

void main(void){
    int n = 0 ;
    scanf("%d",&n);
    int numList[n] = {};
    for(int i = 0 ; i < n ; i++){
        int selectNumber = 0;
        scanf("%d",&selectNumber);
        numList[selectNumber-1]++;
    }

    int count = 0;
    for(int i = 0 ; i < n ; i++){
        if( numList[i] >= 2){
            count += numList[i]/2;
        }
    }
    printf("%d",count);
}