#include <bits/stdc++.h>
int n, i, j, a[105], sum;
int main() {
  scanf("%d", &n);
  for (i = 0; i < n; i++) {
    scanf("%d", &j);
    a[j]++;
  }
  for (i = 1; i <= 100; i++) sum += a[i] / 2;
  printf("%d", sum / 2);
  scanf(" ");
}
