#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-8;
const double pi = acos(-1.0);
int dblcmp(double d) {
  if (fabs(d) < eps) return 0;
  return d > eps ? 1 : -1;
}
int n, a[111], c[111];
int main() {
  int i, j, k, ans = 0;
  int n;
  scanf("%d", &n);
  for (i = 0; i < n; i++) {
    scanf("%d", a + i);
    c[a[i]]++;
  }
  int ok = 1;
  while (ok) {
    ok = 0;
    for (i = 1; i <= 100; i++) {
      if (c[i] >= 4) {
        c[i] -= 4;
        ok = 1;
        ans++;
        break;
      }
    }
    if (ok) continue;
    for (i = 1; i <= 100; i++) {
      for (j = i + 1; j <= 100; j++) {
        if (c[i] >= 2 && c[j] >= 2) {
          c[i] -= 2;
          c[j] -= 2;
          ok = 1;
          ans++;
          break;
        }
      }
      if (ok) break;
    }
  }
  printf("%d\n", ans);
  return 0;
}
