#JSGF V1.0;
grammar simpleNav;
<number> =  1 |  2 |  3 |  4 |  5 |  6 |  7 |  8 |  9 | 10 |
           11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 ;
public <simpleNav> = go back {$ = 'back'} | go to next {$ = 'next'} | <number> {$ = $$};