int getOccurrence(int numbers[], char length);
void ex2() {
    int numbersSequence[] = { 10, 20, 10, 30, 10, 10, 20 };
    char sequenceLength = sizeof(numbersSequence) / sizeof(numbersSequence[0]);

    cout << getOccurrence(numbersSequence, sequenceLength) << endl;
}

int getOccurrence(int numbers[], char length) {
    char res = 0;

    for (char i = 0; i < length; i++) {
        res ^= numbers[i];
    }

    return res;
}

int getMissingNumber(int sequence[], int sequenceLength) {
    int total = (sequenceLength + 1)*(sequenceLength + 2) / 2;

    for (int i = 0; i < sequenceLength; i++) {
        total -= sequence[i];
    }

    return total;
}

void ex3() {
    const char sequenceLength = 5;

    int numbersSequence[sequenceLength] = { 1, 2, 4, 5, 6 };
    int missingNumber = getMissingNumber(numbersSequence, sequenceLength);

    cout << "The missing number in the sequence is " << missingNumber << endl;
}