double getfloat(double *pn) {
	if (pn == NULL)
		return -1;
	int c, sign, flag=1;
	while (isspace(c = getchar()));
	if (!isdigit(c) && c != EOF && c != '+' && c != '-')
	{
		ungetc(c, stdin);
		return 0;
	}
	sign = (c == '-') ? -1 : 1;
	if (c == '-' || c == '+') {
		c = getchar();
		if (!isdigit(c)) {
			ungetc(c, stdin);
			return 0;
		}
	}
	for (*pn = 0;isdigit(c);c = getchar()) {
		*pn = 10 * *pn + (c - '0');
	}
	if (c == '.') {
		c = getchar();
		if (!isdigit(c)) {
			ungetc(c, stdin);
		}
		for (;isdigit(c);c = getchar()) {
			flag *= 10;
			*pn = 10 * *pn + (c - '0');
		}
	}
	*pn = *pn  / flag * sign;
	if (c != EOF)
		ungetc(c, stdin);
	return c;
}