foo.cc: In function 'int main()':
foo.cc:6:5: error: 'ios' has not been declared
     ios::sync_with_stdio(false);
     ^~~
foo.cc:7:2: error: 'cin' was not declared in this scope
  cin.tie();
  ^~~
foo.cc:7:2: note: suggested alternative:
In file included from foo.cc:1:0:
/usr/include/c++/7/iostream:60:18: note:   'std::cin'
   extern istream cin;  /// Linked to standard input
                  ^~~
foo.cc:9:2: error: 'cout' was not declared in this scope
  cout<<a+b<<endl;
  ^~~~
foo.cc:9:2: note: suggested alternative:
In file included from foo.cc:1:0:
/usr/include/c++/7/iostream:61:18: note:   'std::cout'
   extern ostream cout;  /// Linked to standard output
                  ^~~~
foo.cc:9:13: error: 'endl' was not declared in this scope
  cout<<a+b<<endl;
             ^~~~
foo.cc:9:13: note: suggested alternative:
In file included from /usr/include/c++/7/iostream:39:0,
                 from foo.cc:1:
/usr/include/c++/7/ostream:590:5: note:   'std::endl'
     endl(basic_ostream<_CharT, _Traits>& __os)
     ^~~~

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