C++ :

#include<bits/stdc++.h>
using namespace std;
int n;
int main()
{
//	freopen("1.in","r",stdin);
//	freopen("1.out","w",stdout);
	cin>>n;
	if(n%3==0) cout<<n/3;
	else cout<<n/3+1;
    return 0;
}