foo.cc: In function 'int gy(int, int)':
foo.cc:6:6: error: 'ni' was not declared in this scope
   if(ni%i==0&&n2%i==0){
      ^~
foo.cc:6:6: note: suggested alternative: 'i'
   if(ni%i==0&&n2%i==0){
      ^~
      i

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