#include <iostream>
#include <vector>
#include <cstring>
#include <cmath>

#define ll long long

using namespace std;

bool esPrimo(const ll &n)
{
    ll lim = sqrt(n);

    for(ll i = 2; i <= lim; i++)
        if(!(n % i))
            return false;

    return true;
}

int main()
{
    ll n, r = 0;

    cin >> n;

    if(esPrimo(n))
    {
        cout << "1\n";
    }
    else
    {
        for(ll i = 2; i <= sqrt(n); i++)
        {
            if(esPrimo(i) && (!(n % i)))
            {
                r = i;

                break;
            }
        }

        cout << (1 + ((n - r) / 2)) << "\n";
    }

    return 0;
}