関連ワード:  why do you need return 0 in c    why do we need return 0 in c++    why do we use return 0 in cpp    why do you have to return 0 in c++    why do you return 0 in c++    why do we return 0 in c    do i need return 0 in c    why do you have to return 0 in c    is return 0 necessary in c    what happens if we don't use return 0 in c