foo.cc:2:20: error: expected ‘;’ before ‘int’
    2 | using namespace std
      |                    ^
      |                    ;
    3 | int main()
      | ~~~                 
foo.cc: In function ‘int main()’:
foo.cc:6:9: error: expected initializer before ‘cin’
    6 |         cin>>a>>b>>c
      |         ^~~