foo.cc: In function 'int main()':
foo.cc:6:2: error: '__int64' was not declared in this scope
  __int64 x,y;
  ^~~~~~~
foo.cc:6:2: note: suggested alternative: '__int64_t'
  __int64 x,y;
  ^~~~~~~
  __int64_t
foo.cc:7:2: error: 'x' was not declared in this scope
  x = 0;
  ^
foo.cc:11:18: error: 'y' was not declared in this scope
   scanf("%I64d",&y);
                  ^
foo.cc:8:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~

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