读入优化

void Cin(int &x)
{
    char c=getchar();x=0;
    int y=1;
    while(c<'0'||c>'9')
    {
        if(c=='-')
        y=-1;
        c=getchar();
    }
    while(c<='9'&&c>='0')x=x*10+c-'0',c=getchar();
    x*=y;
}