const int IN_LEN = 1 << 22;
char buf[IN_LEN], *front = buf, *back = buf;

inline char fast_getchar() {
	if(front==back){
		front=buf;
		back=buf+fread(buf,1,IN_LEN,stdin);
	}
	return *front++;
}

inline void read(int &in) {
	in = 0;
	bool f = false;
	char c = fast_getchar();
	while (c < '0' || c > '9') {
		if (c == '-') {
			f = true;
		}
		c = fast_getchar();
	}
	while (c >= '0' && c <= '9') {
		in = in * 10 + c - '0';
		c = fast_getchar();
	}
	if (f) {
		in = -in;
	}
}

只会死循环，一点反应都没用。