#include <bits/stdc++.h>
#define int long long
#define fast ios_base::sync_with_stdio(0); cin.tie(NULL); cout.tie(NULL);
#define endl '\n'
#define sp " "
using namespace std;

int32_t main()
{
    fast
    int n;cin>>n;
    int cnt = 0;
    while(n >= 3){
        n -= 3;
        cnt++;
    }
    while(n >= 2){
        n -= 2;
        cnt++;
    }
    cout << cnt;
    return 0;
}