program firstExample {
                    declarations
                    a -> Integer;
                    b -> Integer;
                    c -> Integer;
                    d -> Boolean;
                    
statements
                    a := 1;
                    read c;
                    if(c >= 1) then  {
                                    for(b in a to c) step 2 satisfying (True) {
                                                                             write b;
                                                                              };
                                     }
                               else  {
                                    write -1;
                                     }
                    ;
                     }