i have this code:
<...>
    long x, y;
<...>
    if( (x + y) % 2 == 0 )
        printf("%ld %ld", x, y);
    else
        printf("%ld %ld", y, x);
<...>
and i don't check that x is > 0 and y > 0. Because "Input contains <...> output parameters of the function". so they are greater than 0! Can you explain me what is wrong?

Examine the code again. if x<=0 || y<=0, value of x and y won't change. Maybe you should mention that the function never returns any value. you must output the input parameters based on the value of x and y in the last line of the function.