快读
注意读入到文件结尾才结束，直接运行会无输出。
char buf[1 << 21], *p1 = buf, *p2 = buf;
inline char getc() {return p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 1 << 21, stdin), p1 == p2) ? 0 : *p1++;
}
template<typename T> void Cin(T &a) {T ans = 0;bool f = 0;char c = getc();for (; c < '0' || c > '9'; c = getc()) {if (c == '-') f = -1;}for (; c >= '0' && c <= '9'; c = getc()) {ans = ans * 10 + c - '0';}a = f ? -ans : ans;
}
template<typename T, typename... Args> void Cin(T &a, Args &...args) {Cin(a), Cin(args...);
}
template<typename T> void Cout(T x) { // 注意，这里输出不带换行if (x < 0) putchar('-'), x = -x;if (x > 9) Cout(x / 10);putchar(x % 10 + '0');
}