foo.c: In function 'main':
foo.c:5:5: error: 'cin' undeclared (first use in this function)
    5 |     cin>>a>>b>>c;
      |     ^~~
foo.c:5:5: note: each undeclared identifier is reported only once for each function it appears in
foo.c:6:12: error: 'cout' undeclared (first use in this function)
    6 |     printf(cout<<a<<""<<b<<""<<c<<endl;//321);
      |            ^~~~
foo.c:6:35: error: 'endl' undeclared (first use in this function)
    6 |     printf(cout<<a<<""<<b<<""<<c<<endl;//321);
      |                                   ^~~~
foo.c:6:39: error: expected ')' before ';' token
    6 |     printf(cout<<a<<""<<b<<""<<c<<endl;//321);
      |           ~                           ^
      |                                       )
foo.c:6:5: error: expected declaration or statement at end of input
    6 |     printf(cout<<a<<""<<b<<""<<c<<endl;//321);
      |     ^~~~~~

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