Counter

#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <climits>

typedef long long ll;

using namespace std;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    // freopen("input.txt", "r", stdin); // TODO: REMOVE THIS YOU STUPID ****

    int n;
    cin >> n;
    if (n == 0) {
        cout << 0;
        return 0;
    }
    if (n < 11) {
        cout << -1;
        return 0;
    }
    int a = n / 11;
    int rest = n % 11;
    if (rest == 0) {
        cout << a;
        return 0;
    }
    if ((11-rest) % 2 != 0) {
        cout << -1;
        return 0;
    }
    int c = (11 - rest) / 2;
    cout << a + c + 1;
    return 0;
}

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: WRONG ANSWER

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: WRONG ANSWER

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: WRONG ANSWER

Test 20

Verdict: WRONG ANSWER

Test 21

Verdict: WRONG ANSWER

Test 22

Verdict: ACCEPTED

Test 23

Verdict: WRONG ANSWER

Test 24

Verdict: WRONG ANSWER

Test 25

Verdict: ACCEPTED

Test 26

Verdict: WRONG ANSWER

Test 27

Verdict: ACCEPTED