读入加速
namespace IO {
const static int maxn = 10e7;
static char buf[maxn], *pbuf = buf, *End;
void init() {
int c = fread(buf, 1, maxn, stdin);
End = buf + c;
}
int &readint() {
static int ans;
ans = 0;
while (pbuf != End && !isdigit(*pbuf)) pbuf ++;
while (pbuf != End && isdigit(*pbuf)) {
ans = ans * 10 + *pbuf - '0';
pbuf ++;
}
return ans;
}
}