foo.c: In function ‘main’:
foo.c:5:9: error: ‘cin’ undeclared (first use in this function)
    5 |         cin>>a>>b>>c;
      |         ^~~
foo.c:5:9: note: each undeclared identifier is reported only once for each function it appears in
foo.c:7:17: error: ‘cout’ undeclared (first use in this function)
    7 |                 cout<<a<<"<"<<b<<"<"<<c<<endl;
      |                 ^~~~
foo.c:7:42: error: ‘endl’ undeclared (first use in this function)
    7 |                 cout<<a<<"<"<<b<<"<"<<c<<endl;
      |                                          ^~~~
foo.c:13:23: error: ‘C’ undeclared (first use in this function)
   13 |                 cout<<C<<"<"<<a<<"<"<<b<<endl;
      |                       ^
foo.c:14:9: error: ‘else’ without a previous ‘if’
   14 |         else
      |         ^~~~
foo.c:19:18: warning: statement with no effect [-Wunused-value]
   19 |                 b<a a>c
      |                 ~^~
foo.c:19:20: error: expected ‘;’ before ‘a’
   19 |                 b<a a>c
      |                    ^~
      |                    ;
foo.c:22:9: error: ‘else’ without a previous ‘if’
   22 |         else
      |         ^~~~
foo.c:23:46: error: expected ‘;’ before ‘return’
   23 |                 cout<<c<<"<"<<b<<"<"<<a<<endl
      |                                              ^
      |                                              ;
   24 | return 0;
      | ~~~~~~