foo.c:1:1: error: stray '##' in program
    1 | ##include <iostream>
      | ^~
foo.c:1:11: error: expected '=', ',', ';', 'asm' or '__attribute__' before '<' token
    1 | ##include <iostream>
      |           ^
foo.c:2:10: fatal error: cstdio: No such file or directory
    2 | #include <cstdio>
      |          ^~~~~~~~
compilation terminated.

[Hydro](https://hydro.ac)提供评测服务