/* compile with -DV for volatile, -UV for not volatile */

#ifdef V
#define VOLATILE volatile
#else
#define VOLATILE
#endif

extern VOLATILE char wants_to_enter[2];
extern VOLATILE char turn;
extern VOLATILE long counter;

#define me 0
#define other (1-me)

void p(void) {
    wants_to_enter[me] = 1;
    while (wants_to_enter[other]) {
        if (turn != me) {
            wants_to_enter[me] = 0;
            while (turn != me) {}
            wants_to_enter[me] = 1;
	}
    }
    counter++;
    turn = other;
    wants_to_enter[me] = 0;
}