#include<bits/stdc++.h>
using namespace std;
int main(){
    int n;cin>>n;
    int ans = 0;
    if(n%3==0)ans = n/3;
    else if(n%2==0)ans = n/2;
    else{
        n = n-3;
        ans+=1;
        ans += n/2;

    }
    cout<<ans<<endl;
    return 0;
}