快速读入fread

struct FastIO {

    static const int S = 1e7;

    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 = fread(buf, 1, S, stdin);

        if (pos == len) exit(0);

        return buf[pos++];

    }

    inline int xuint() {

        int c = xchar(), x = 0;

        while (c <= 32) c = xchar();

        for (; '0' <= c && c <= '9'; c = xchar()) x = x * 10 + c - '0';

        return x;

    }

    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;

    }

    inline void xstring(char *s)

    {

        int c = xchar();

        while (c <= 32) c = xchar();

        for (; c > 32; c = xchar()) * s++ = c;

        *s = 0;

    }

    inline void wchar(int x)

    {

        if (wpos == S) fwrite(wbuf, 1, S, stdout), wpos = 0;

        wbuf[wpos++] = x;

    }

    inline void wint(ll x)

    {

        if (x < 0) wchar('-'), x = -x;

        char s[24];

        int n = 0;

        while (x || !n) s[n++] = '0' + x % 10, x /= 10;

        while (n--) wchar(s[n]);

        wchar('\n');

    }

    inline void wstring(const char *s)

    {

        while (*s) wchar(*s++);

    }

    ~FastIO()

    {

        if (wpos) fwrite(wbuf, 1, wpos, stdout), wpos = 0;

    }

} io;