foo.cc: In function 'int main()':
foo.cc:6:1: error: 'cout' was not declared in this scope
 cout<<"依次输入a,b,c的值，用空格或者回车分开"<<endl;
 ^~~~
foo.cc:6:1: note: suggested alternative:
In file included from foo.cc:2:0:
/usr/include/c++/7/iostream:61:18: note:   'std::cout'
   extern ostream cout;  /// Linked to standard output
                  ^~~~
foo.cc:6:64: error: 'endl' was not declared in this scope
 cout<<"依次输入a,b,c的值，用空格或者回车分开"<<endl;
                                                                ^~~~
foo.cc:6:64: note: suggested alternative:
In file included from /usr/include/c++/7/iostream:39:0,
                 from foo.cc:2:
/usr/include/c++/7/ostream:590:5: note:   'std::endl'
     endl(basic_ostream<_CharT, _Traits>& __os)
     ^~~~
foo.cc:7:1: error: 'cin' was not declared in this scope
 cin>>a>>b>>c;
 ^~~
foo.cc:7:1: note: suggested alternative:
In file included from foo.cc:2:0:
/usr/include/c++/7/iostream:60:18: note:   'std::cin'
   extern istream cin;  /// Linked to standard input
                  ^~~

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