[其他] 看看这个程序错在哪里

#include<iostream.h>
class B
{public:
B(int x)
{a=x;
cout<<"调用构造函数,a="<<a<<endl;
}

void print()
{cout<<"a="<<a<<endl;}
B()
{ a = 0;cout<<"调用构造函数,a="<<a<<endl;}
private:
int a;
};

void main()
{int x=17;
B a1(3),a2,a3[1];
a1=B(7);
a1.print();a2.print();
for(int i=0;i<1;i++)
{a3[0]=B(i+1);a3[0].print();}
cout<<" main()\n";
}