#include <bits/stdc++.h>
int main() {
  int p[105];
  memset(p, 0, sizeof(p));
  int n, t, i;
  scanf("%d", &n);
  while (n--) {
    scanf("%d", &t);
    p[t]++;
  }
  for (t = 0, i = 1; i <= 100; i++) {
    t = t + p[i] / 2;
  }
  t = t / 2;
  printf("%d\n", t);
  return 0;
}
