#include <iostream>
#include <bits/stdc++.h>
#include <algorithm>
#include <vector>
#include <map>
using namespace std;



int main(){
    int n;
    cin >> n;
    int p[n];
    rep(i,0,n){
        cin >> p[i+1];
    }
    cout << n/2 << endl;
    //--------------
    return 0;
}