#include<bits/stdc++.h>
using namespace std;

int main(){
    int N,in,ans=0;
    cin >> N;
    vector<int> v(10,0);

    while(cin >> in){
        if(++v[in-1]==2){
            v[in-1]=0;
            ans++;
        }
    }

    ans+=accumulate(v.begin(),v.end(),0)/4;
    cout << ans << endl;

    return 0;
}