/in/foo.c:1:1: error: unknown type name 'using'
    1 | using System;
      | ^~~~~
/in/foo.c:2:1: error: unknown type name 'using'
    2 | using System.Linq;
      | ^~~~~
/in/foo.c:2:13: error: expected '=', ',', ';', 'asm' or '__attribute__' before '.' token
    2 | using System.Linq;
      |             ^
/in/foo.c:4:1: error: unknown type name 'class'
    4 | class Program {
      | ^~~~~
/in/foo.c:4:15: error: expected '=', ',', ';', 'asm' or '__attribute__' before '{' token
    4 | class Program {
      |               ^