请帮我看看为何在输入回车以后程序不能执行倒数第二行？

Question

#include
#include "Sales_item.h"

int main(){
Sales_item item, addItem;
std::cout << std::endl;
std::cin >> item;
while (std::cin >> addItem)
item += addItem;
std::cout<<"The sum of this books is "<<item<<std::endl;
return 0;
}

PS：鄙人C++之极品菜鸟，请使劲喷。