/in/foo.cc: In function 'int main()':
/in/foo.cc:5:16: warning: unused variable 'a1' [-Wunused-variable]
  int n,a[1009],a1[1009],a2[1009];
                ^~
/in/foo.cc:5:25: warning: unused variable 'a2' [-Wunused-variable]
  int n,a[1009],a1[1009],a2[1009];
                         ^~