std::rand() function gives back unproper results

I have simply functions to random numbers but there is something wrong with the first one because the results are not correct.

 int wylosuj(int a, int b)
{
    int wynik=(( std::rand() % b-a+1 ) + a);
    return wynik;
}

Second Function (this one gives me the proper result)

int wylosuj(int a, int b)
{
int endNumber=b-a+1;
int startNumber=a;
return std::rand()%endNumber+startNumber;
}

In my main function I have got this line to run the function with arguments:

wylosuj(3,3);

So desired results should be only 3.

Where did I make mistake with first function?