#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define repp(i, n) rep(i, 0, n)
#define repb(i, a, b) for(int i = a; i >= b; i--)
#define all(a) a.begin(), a.end()
#define int long long
using namespace std;
typedef pair<int, int> P;

signed main(){
    int a, ans = -1;
    cin >> a;
    rep(i, 8, 100){
        if(i + 7 == a){
            ans = i; break;
        }
    }
    cout << ans << endl;
}