foo.c: In function ‘main’:
foo.c:6:9: error: ‘cin’ undeclared (first use in this function)
    6 |         cin     >> a >>b >>c;
      |         ^~~
foo.c:6:9: note: each undeclared identifier is reported only once for each function it appears in
foo.c:10:25: error: ‘cout’ undeclared (first use in this function)
   10 |                 if(b>c) cout << a << " " << b << " " << c;
      |                         ^~~~
foo.c:11:55: error: expected ‘;’ before ‘:’ token
   11 |                 else cout << a << " " << c << " " << b:
      |                                                       ^
      |                                                       ;