int
fsm_main(const char *s)
{
	const char *p;

	enum {
		S0, S1, S2, S3, S4, S5, S6, S7, S8, S9, 
		S10, S11, S12
	} state;

	state = S0;

	for (p = s; *p != '\0'; p++) {
		switch (state) {
		case S0: /* start */
			switch ((unsigned char) *p) {
			case 'N': state = S1; break;
			case 'O': state = S2; break;
			case 'F': state = S3; break;
			default:  return -1; /* leaf */
			}
			break;

		case S1: /* e.g. "N" */
			switch ((unsigned char) *p) {
			case 'e': state = S12; break;
			default:  return -1; /* leaf */
			}
			break;

		case S2: /* e.g. "O" */
			switch ((unsigned char) *p) {
			case 'p': state = S10; break;
			default:  return -1; /* leaf */
			}
			break;

		case S3: /* e.g. "F" */
			switch ((unsigned char) *p) {
			case 'r': state = S4; break;
			default:  return -1; /* leaf */
			}
			break;

		case S4: /* e.g. "Fr" */
			switch ((unsigned char) *p) {
			case 'e': state = S5; break;
			default:  return -1; /* leaf */
			}
			break;

		case S5: /* e.g. "Fre" */
			switch ((unsigned char) *p) {
			case 'e': state = S6; break;
			default:  return -1; /* leaf */
			}
			break;

		case S6: /* e.g. "Net" */
			switch ((unsigned char) *p) {
			case 'B': state = S7; break;
			default:  return -1; /* leaf */
			}
			break;

		case S7: /* e.g. "NetB" */
			switch ((unsigned char) *p) {
			case 'S': state = S8; break;
			default:  return -1; /* leaf */
			}
			break;

		case S8: /* e.g. "NetBS" */
			switch ((unsigned char) *p) {
			case 'D': state = S9; break;
			default:  return -1; /* leaf */
			}
			break;

		case S9: /* e.g. "NetBSD" */
			return -1; /* leaf */

		case S10: /* e.g. "Op" */
			switch ((unsigned char) *p) {
			case 'e': state = S11; break;
			default:  return -1; /* leaf */
			}
			break;

		case S11: /* e.g. "Ope" */
			switch ((unsigned char) *p) {
			case 'n': state = S6; break;
			default:  return -1; /* leaf */
			}
			break;

		case S12: /* e.g. "Ne" */
			switch ((unsigned char) *p) {
			case 't': state = S6; break;
			default:  return -1; /* leaf */
			}
			break;

		default:
			; /* unreached */
		}
	}

	/* end states */
	switch (state) {
	case S9: return 0x1; /* "(Net|Open|Free)BSD" */
	default: return -1; /* unexpected EOT */
	}
}