You just map the value (1, 1) to the value 1 of , and it works out. E.g. for , the group generated by of (1, 1) is:
0 = (0, 0)
1 = (1, 1)
2 = (0, 2)
3 = (1, 0)
4 = (0, 1)
5 = (1, 2)
6 = (0, 0) = 0