/in/foo.cc: In function 'int main()':
/in/foo.cc:24:20: error: 'fa' was not declared in this scope
   if(st[i].avg>80&&fa>0)
                    ^~
/in/foo.cc:30:25: error: 'xi' was not declared in this scope
   else if(st[i].avg>85&&xi)
                         ^~
/in/foo.cc:43:41: error: request for member 'sum' in 'maxXia', which is of non-class type 'int'
  cout<<st[maxXia].name<<endl<<st[maxXia.sum]<<endl<<zong;
                                         ^~~