Writing 2D array into a file using function in C

void IspisMatriceUDatoteku(int red, int stupac, int *matrica)
{
    FILE *f;
    char imeDatoteke[50];

    printf("\nUnesite ime datoteke :");
    scanf("%s", imeDatoteke);
    f = fopen(imeDatoteke, "w");

    if(NULL == f)
        printf("Nevalja!!!\n");
    else
    {
        for(int i=0; i<red; i++)
            {
                for(int j=0; j<stupac; j++)
                {
                    fflush(f);
                    fprintf(f, "%d ", matrica[i*stupac+j]);
                }
                fprintf(f ,"\n");
            }
    }
}


 int main()
 {
    int red, stupac;
    int *a=NULL;
    printf("Unesite dimenzije matrice :");//matrix dimensions rows and columns
    scanf("%d %d", &red, &stupac);
    a = (int*)malloc(red* stupac* sizeof(int));

    IspisMatriceUDatoteku(red, stupac, a);
 }

I'm trying to write matrix into a file. If i try to put :

9 8 8 
6 1 8 
4 3 8

into a file using this code i get :

9 8 8 
6 1 8 
4 3 

So my question is how to get that last element into my file using function like this or there is another way to write matrix inside it. Matrix is randomly generated in another function. Thanks.