text: #include "types.h"
  #include "user.h"
  #include "stat.h"
  
  #define NULL ((void *)0)
  
  int main(int argc, char *argv[]) {
  	int *a = NULL;
  	int b = *a;
  	b = b + 1;
  	printf(1,"null ptr dereference %d\n", b);
  	exit();
  }
  