#include <bits/stdc++.h>
#include <vector>
#define MAX_INF 0x999
using namespace std;

int main() {
    int n;
    int ans = 0;
    cin >> n;
    vector<int> dp(n + 1, MAX_INF);
    dp[0] = 0;
    vector<int > nums;
    nums.push_back(6);
    nums.push_back(8);
    for (int i = 1; i <= n; i++) {
        for (int j = 0; j < nums.size(); j++) {
            if (nums[j] <= i) {
                dp[i] = min(dp[i], dp[i - nums[j]] + 1);
            }
        }
    }
    int res = dp[n] == MAX_INF ? -1 : dp[n];
    cout << res;
    return 0;
}
// 64 位输出请用 printf("%lld")