Puzzle P28

Puzzle P28 — Changing a Pointer to a Pointer

Of course, a pointer to a pointer can be changed to point to a new thing:

#include  <stdio.h> 

void main ( void )
{
  int value = 77, num = 99 ;
  int *pv= &value, *pn = &num ;
  int **ppi ;

  ppi = &pv;
  printf("**ppi = %d\n", **ppi );

  ppi = &pn;
  printf("**ppi = %d\n", **ppi );

}

What does the program write?