関連ワード:  why do we return 0 in c++    why do we return 0 in cpp    why do we need return 0 in c++    why do we use return 0 in c++    why do we write return 0 in cpp    what does return 0 in c++    what is return 0 in c++    what is the point of return 0 in c++    why we use return 0 in c++    why we write return 0 in c++