Counter

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef vector<ll> vl;
typedef pair<ll,ll> pl;


typedef long double C;
typedef complex<C> P;
#define X real()
#define Y imag()

#define sz(x) (ll)(x).size()

#define F first
#define S second
#define PB push_back
#define MP make_pair

#define REP(i,a,b) for (ll i = a; i < b; i++)


int main() {
    ll x;
    cin >> x;

    ll cnt = 0;
    ll move= 0;
    while(true) {
        if(cnt == x) {
            cout << move << endl;
            return 0;
        }

        if(cnt < 0) {
            cout << -1 << endl;
            return 0;
        }

        if(cnt + 11 > x) {
            cnt = cnt-2;
            move++;
        } else {
            cnt += 11;
            move++;
        }
    }
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED