#include <stdlib.h>
#include <stdio.h>

enum states {
	START,
	LOOP,
	END,
} state;

enum events {
	START_LOOPING,
	PRINT_HELLO,
	STOP_LOOPING,
};

void step_state(enum events event) {
	switch(state) {
	case START:
		switch(event) {
		case START_LOOPING:
			state = LOOP;
			break;
		default:
			exit(1);
			break;
		}
		break;
	case LOOP:
		switch(event) {
		case PRINT_HELLO:
			printf("Hello World!\n");
			break;
		case STOP_LOOPING:
			state = END;
			break;
		default:
			exit(1);
			break;
		}
		break;
	case END:
		exit(1);
		break;
	}
}

int main(void) {
	step_state(START_LOOPING);
	step_state(PRINT_HELLO);
	step_state(PRINT_HELLO);
	step_state(STOP_LOOPING);
	return 0;
}