foo.cc:7:12: error: stray '#' in program
  if(x == 2)#include "iostream"
            ^
foo.cc: In function 'int Prime(int)':
foo.cc:7:13: error: 'include' was not declared in this scope
  if(x == 2)#include "iostream"
             ^~~~~~~
foo.cc:23:1: error: a function-definition is not allowed here before '{' token
 {
 ^
foo.cc:32:1: error: a function-definition is not allowed here before '{' token
 {
 ^

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。