输入挂（板子）

struct FastIO {
    static const int S = 1000 << 1;
    int wpos;
    char wbuf[S];
    FastIO() : wpos(0) {}
    inline int xchar() {
        static char buf[S];
        static int len = 0, pos = 0;
        if (pos == len) {
            pos = 0;
            len = (int)fread(buf, 1, S, stdin);
        }
        if (pos == len) {
            return -1;
        }
        return buf[pos++];
    }
    inline int xint() {
        int s = 1, c = xchar(), x = 0;
        while (c <= 32) {
            c = xchar();
        }
        if (c == '-') {
            s = -1;
            c = xchar();
        }
        for (; '0' <= c && c <= '9'; c = xchar()) {
            x = x * 10 + c - '0';
        }

        return x * s;
    }
    ~FastIO() {
        if (wpos) {
            fwrite(wbuf, 1, wpos, stdout);
            wpos = 0;
        }
    }
} io;

class Reader
{
public:
    inline char nc();
    template<class T> inline void read(T &x);
    template<class T> inline Reader& operator >> (T &x) { read(x); return *this; }
} rd;

inline char Reader::nc()
{
    static char buf[100000], *p1=buf, *p2=buf;
    if (p1 == p2) { p2 = (p1 = buf) + fread(buf, 1, 100000, stdin); if (p1 == p2) exit(0); }
    return *p1++;
}

template<class T> inline void Reader::read(T &x)
{
    char c = nc(); bool b = 0;
    for (; !(c >= '0' && c <= '9'); c = nc()) if (c == '-') b = 1;
    for (x = 0; c >= '0' && c <= '9'; x = x * 10 + c - '0',c = nc());
    if(b) x = -x;
}