Hi folks. I have a dataset of this form:

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input float(id dist wc)
1 60 3
1 90 2
1 10 3
1 30 1
1 90 3
1 10 2
1 10 4
1 60 3
1 90 1
2 90 2
2 50 2
2 10 3
2 60 1
2 30 4
2 30 1
2 90 3
2 10 2
2 40 3
end
and I would like to make a variable "id2" that takes on the value 1 for observations 1-3, 2 for observations 4-6, etc. This is the format I would like:

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input float(id id2 dist wc)
1 1 60 3
1 1 90 2
1 1 10 3
1 2 30 1
1 2 90 3
1 2 10 2
1 3 10 4
1 3 60 3
1 3 90 1
2 4 90 2
2 4 50 2
2 4 10 3
2 5 60 1
2 5 30 4
2 5 30 1
2 6 90 3
2 6 10 2
2 6 40 3
end
Any idea how to do this? It's probably an easy fix, but I can't figure it out. Thank you so much!