/in/foo.cc: In function 'void MakeHeap(int*, int)':
/in/foo.cc:17:4: error: 'flag' was not declared in this scope
    flag=a[i];
    ^~~~
/in/foo.cc:9:10: warning: unused variable 'temp' [-Wunused-variable]
  int i,j,temp;
          ^~~~