Use of C + + const

What does the following statement mean?
const int A;
int const A;
const int *a;
int * const A;
int const * a const;

1, A is a constant number of plastic

2, A is a constant number of plastic

3, A is a pointer to the number of normal shaping (the number of shapes can not be modified, the pointer can be modified)

4, A is a constant pointer to the number of shapes (shaping number can be modified, the pointer is not modifiable)

5, A is a constant pointer to the number of constant shaping (two can not be modified)

Use of C + + const