#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define ll long long
#define ld long double
#define ull unsigned long long
#define lcm(a,b) ((a*b)/__gcd(a,b))
const int MOD = 1000000007;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    
    int n;
    cin >> n;

    if (n % 3 == 0){
        cout << n / 3 << endl;
    }
    else if (n % 3 == 1){
        int s1 = n / 3 - 1;
        s1 = max(0, s1);
        
        cout << s1 + 2 << endl;
    }
    else if (n % 3 == 2){
        int s1 = n / 3;
        cout << s1 + 1 << endl;
    }
}