/in/foo.cc: In function 'int main()':
/in/foo.cc:4:19: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
 #define fo(i,j,k) for (int i=(j);i<=(k);i++)
                   ^
/in/foo.cc:36:3: note: in expansion of macro 'fo'
   fo(i,0,2*n-1) printf("%d ",ans[i]+1);printf("\n");
   ^~
/in/foo.cc:36:40: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
   fo(i,0,2*n-1) printf("%d ",ans[i]+1);printf("\n");
                                        ^~~~~~