读入优化

inline void read(int &x){
    x=0;char c=getchar();bool f=0;
    if(c=='-')f=1;
    while(c<'0'||c>'9') c=getchar();
	while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();}
	if(f==1)x=-x;
}