我也学会快读了~~~
没啥可讲的
注意对负号的处理

int input () {int x = 0, f = 0;char c = getchar ();while (c < '0' || c > '9') f = c == '-', c = getchar ();while (c >= '0' && c <= '9') x = (x << 1) + (x << 3) + (c ^ 48), c = getchar ();return f ? - x : x;
}