// ----------------First example-------------------------
    int num = 4;
    *(*(mat + num / 4) - 3) = 1; // mat[0][0] = 1
    *(*(mat + num / 4) - 2) = 2; // mat[0][1] = 2
    *(*(mat + num / 4) - 1) = 3; // mat[0][2] = 3
    *(*(mat + num / 4)) = 4;     // mat[1][0] = 4
    *(*(mat + num / 4) + 1) = 5; // mat[1][1] = 5
    *(*(mat + num / 4) + 2) = 6; // mat[1][2] = 6

    *(*(mat + (num / 4)) + 3) = 7; // mat[2][0] = 7
    *(*(mat + (num / 4) + 1)) = 7; // mat[2][0] = 7

    *(*(mat + (num / 4)) + 4) = 8;     // mat[2][1] = 8
    *(*(mat + (num / 4) + 2) - 2) = 8; // mat[2][1] = 8

    *(*(mat + (num / 4)) + 5) = 9;     // mat[2][2] = 9
    *(*(mat + (num / 4) + 3) - 4) = 9; // mat[2][2] = 9


// ----------------Second example-------------------------

    int num = 4;
    *((*mat + num / 4) - 1) = 1; // mat[0][0] = 1
    *((*mat + num / 4)) = 2;     // mat[0][1] = 2
    *((*mat + num / 4) + 1) = 3; // mat[0][2] = 3
    *((*mat + num / 4) + 2) = 4; // mat[1][0] = 4
    *((*mat + num / 4) + 3) = 5; // mat[1][1] = 5
    *((*mat + num / 4) + 4) = 6; // mat[1][2] = 6
    *((*mat + num / 4) + 5) = 7; // mat[2][0] = 7
    *((*mat + num / 4) + 6) = 8; // mat[2][1] = 8
    *((*mat + num / 4) + 7) = 9; // mat[2][2] = 9


// ----------------Third example-------------------------
    int num = 4;
    *(mat[(num % 4)]) = 1;          // mat[0][0] = 1
    *(mat[(num % 4)] + 1) = 2;      // mat[0][1] = 2
    *(mat[(num % 4)] + 2) = 3;      // mat[0][2] = 3
    *(mat[(num / 4)]) = 4;          // mat[1][0] = 4
    *(mat[(num / 4)] + 1) = 5;      // mat[1][1] = 5
    *(mat[(num / 4)] + 2) = 6;      // mat[1][2] = 6
    *(mat[(num / 4) + 1]) = 7;      // mat[2][0] = 7
    *(mat[(num / 4) + 1] + 1) = 8;  // mat[2][1] = 8
    *(mat[(num / 4) + 1] + 2) = 9;  // mat[2][1] = 8

/* 
Output of all exmaples: 
_____________________________
1 2 3 
4 5 6 
7 8 9 

*/