foo.cc:6:16: error: '::main' must return 'int'
 long long main()
                ^
foo.cc: In function 'int main()':
foo.cc:12:22: error: cannot convert 'long long int*' to 'int*' for argument '1' to 'long long int getmaxprofit(int*, int)'
  max=getmaxprofit(a,n);
                      ^

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