#include<iostream>
using namespace std;
void mian()
{ int month;
int day;
char retry;
do
{ cout<<"请输入您的出生月份\n";
cin>>month;
cout<<"请问您出生于"<<month<<"几号？\n";
cin>>day;
if ((day>31)||(month>12)||((month=2)&&(day>29))||(((month=4)||(month=6)||(month=9)||(month=11))&&(day>30)))
cout<<"您输入的是错误的日期\n";
else if(((month==3)&&(21<=day)&&(day<=31))||((month==4)&&(1<=day)&&(day<=19)))
cout<<"您的星座为白羊座，属性火\n";
else if(((month==4)&&(20<=day)&&(day<=30))||((month==5)&&(1<=day)&&(day<=20)))
cout<<"您的星座为金牛座，属性土\n";
else if(((month==5)&&(21<=day)&&(day<=31))||((month==6)&&(1<=day)&&(day<=21)))
cout<<"您的星座为双子座，属性气\n";
else if(((month==6)&&(22<=day)&&(day<=30))||((month==7)&&(1<=day)&&(day<=22)))
cout<<"您的星座为巨蟹座，属性水\n";
else if(((month==7)&&(23<=day)&&(day<=31))||((month==8)&&(1<=day)&&(day<=22)))
cout<<"您的星座为狮子座，属性火\n";
else if(((month==8)&&(23<=day)&&(day<=31))||((month==9)&&(1<=day)&&(day<=22)))
cout<<"您的星座为处女座，属性土\n";
else if(((month==9)&&(23<=day)&&(day<=30))||((month==10)&&(1<=day)&&(day<=22)))
cout<<"您的星座为天平座，属性气\n";
else if(((month==10)&&(23<=day)&&(day<=31))||((month==11)&&(1<=day)&&(day<=21)))
cout<<"您的星座为天蝎座，属性水\n";
else if(((month==11)&&(22<=day)&&(day<=30))||((month==12)&&(1<=day)&&(day<=21)))
cout<<"您的星座为射手座，属性气\n";
else if(((month==12)&&(22<=day)&&(day<=31))||((month==1)&&(1<=day)&&(day<=19)))
cout<<"您的星座为魔杰座，属性土\n";
else if(((month==1)&&(20<=day)&&(day<=31))||((month==2)&&(1<=day)&&(day<=18)))
cout<<"您的星座为水瓶座，属性气\n";
else
cout<<"您的星座为双鱼座，属性水\n";
cout<<"您是否要重新输入您的生日，“是”请输入Y,“否”请输入N\n";
cin>>retry;
}while(retry=='y'||retry=='Y');
}
麻烦大家看看我这段代码有什么问题吗？
为什么我每次编译都会提示“C++fatal error LNK1561: 必须定义入口点”
抱歉，没有多更多的分了，还望见谅。