87. 有如下程序：
#include<iostream>
using namespace std;
class test{
private:
int a;
public:
test(){cout<<"constructor"<<endl;}
test(int a){cout<<a<<endl;}
test(const test &_test)
{
a=_test.a;
cout<<"copy constructor"<<endl;
}
~test(){cout<<"destructor"<<endl;}
};
int main()
{
test A(3);
return 0;
}
运行时输出的结果是______。
