LONGLONG, __int64如何输入输出

__int64 n(20000000);
scanf("%I64d",&n)
printf("%I64d",n);

//cout,cin无能为力，除非移位操作，分高位和低位操作
ostream & operator<<(ostream &os,__int64 n)
{
return os<<(long)(n&0xFFFFFFFF)<<(long)(n>>32);
}
cout<<n<<endl;
//cin __int64 写法较复杂，不过也经常不用，忽略