foo.c:2:1: error: unknown type name ‘using’
    2 | using namespace std;
      | ^~~~~
foo.c:2:17: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘std’
    2 | using namespace std;
      |                 ^~~
foo.c: In function ‘main’:
foo.c:10:45: error: expected ‘;’ before ‘else’
   10 |                     printf("%d %d %d",a,b,c)
      |                                             ^
      |                                             ;
   11 |                 else
      |                 ~~~~                         
foo.c:19:49: error: expected ‘;’ before ‘else’
   19 |                         printf("%d %d %d",b,a,c)
      |                                                 ^
      |                                                 ;
   20 |                 else
      |                 ~~~~