#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n;
    while(cin >> n)
    {
        if(n<3)cout << 0 << endl;
        else if(n<6)cout << 1 << endl;
        else {
           cout << n/3 << endl; 
        }
    }
    return 0;
}

#define _USE_MATH_DEFINES //M_PI, M_E
#include<bits/stdc++.h>
#define mod 1000000007
#define ll long long int
#define ar array
#define pb push_back
ll power(ll a,ll b){ll r=1;for(;b;b>>=1){if(b&1)r=r*a%mod;a=a*a%mod;}return r;}
using namespace std;

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(NULL);
	int n;
	cin>>n;
	cout<<n/3<<endl;
	return 0;
}