#include <bits/stdc++.h>
int main() {
  int s[110];
  int n, i, ls, sum = 0;
  memset(s, 0, sizeof(s));
  scanf("%d", &n);
  for (i = 0; i < n; i++) {
    scanf("%d", &ls);
    s[ls]++;
  }
  for (i = 0; i < 110; i++) {
    sum += (s[i] / 2);
  }
  printf("%d\n", sum / 2);
  return 0;
}
