bool turn, flag[2];
bool critical0 = 0;
bool critical1 = 0;

active proctype user0()
{
  int pi = 0;
again:
  flag[0] = 1;
  turn = 1;
  (flag[1] == 0 || turn == 0);
  
  critical0 = 1;
  /* critical section */
  critical0 = 0;

  flag[0] = 0;
  goto again;   
}

active proctype user1()
{
  int pi = 1;
ag:
  flag[1] = 1;
  turn = 0;
  (flag[0] == 0 || turn == 1);
  
  critical1 = 1;
  /* critical section */
  critical1 = 0;

  flag[1] = 0;
  goto ag;   
}

active proctype monitor() {
	assert(!(critical0 && critical1));
}

/** TO RUN USE:
 *
 * spin -a peterson.pml
 * gcc pan.c -o pan
 * pan
 *
 * SHOULD REPORT 0 ERRORS
 */