#include<bits/stdc++.h>
#define endl        '\n'
#define F           first
#define S           second
#define pb          push_back
#define yes         cout<<"YES\n"
#define no          cout<<"NO\n"
#define all(x)      x.begin(),x.end()
#define allr(x)     x.rbegin(),x.rend()
#define error1(x)   cerr<<#x<<" = "<<(x)<<endl
#define error2(a,b) cerr<<"("<<#a<<", "<<#b<<") = ("<<(a)<<", "<<(b)<<")\n";
#define coutall(v)  for(auto &it: v) cout << it << " "; cout << endl;
using namespace std;
using ll = long long;
using ld = long double;

vector<ll> divisor(ll n) // O(sqrt(n));
{
    vector<ll> dv; 
    for (ll i = 1; i * i <= n; i++) {
        if (n % i == 0) {
            dv.push_back(i);
            if (i != n / i) dv.push_back(n / i);
        }
    }
    // sort(dv.begin(), dv.end());
    return dv;
}

void solve() {
    ll n, ans = 0;
    cin >> n;
    if(n & 1) ans = 1 + (n - 3) / 2;
    else ans = n / 2;
    // cout << ans << endl;
    ll i = 2;
    while(n - 6 >= 0 && (n - 6) % 2 == 0) {
        ans = min(ans, i + ((n - 6) / 2));
        n -= 3;
        i += 2;
        // cout << n << " ";
    }
    cout << ans << endl;
    return;
}

signed main() {
    ios::sync_with_stdio(false); cin.tie(0);
    int tc = 1;
    // cin >> tc;
    for (int t = 1; t <= tc; t++) {
        // cout << "Case " << t << ": ";
        solve();
    }
    return 0;
}