#include<bits/stdc++.h>
#include<atcoder/all>
#define chmin(x,y) (x) = min((x),(y))
#define chmax(x,y) (x) = max((x),(y))
using namespace std;
using namespace atcoder;
using ll = long long;
const ll mod = 998244353;
using mint = modint998244353;
using Graph = vector<vector<int>>;

int main(){
  // input
  int N; cin >> N;
  vector<int> A(N), B(N+1);
  for(int i = 0; i < N; i++){
    cin >> A[i];
    B[A[i]]++;
  }
  int ans = 0;
  for(int i = 0; i <= N; i++)
    ans += B[i] / 2;
  
  cout << ans << endl;
  // solve
  
  
  // output
}