char* partlyConcat(char firstStr[15], char secondStr[15], int k)
{
    char* result = new char[30];

    int end = 0;
    for (end = 0; firstStr[end] != '\0'; end++);

    end = end - k - 1;

    int index = 0;
    for (index; index <= end; index++)
    {
        result[index] = firstStr[index];
    }

    for (size_t i = 0; i < k; i++)
    {
        result[index++] = secondStr[i];
    }
    result[index] = '\0';

    return result;
}