I would like to generate a new ID variable, which is based on ID1 and ID2. Instead of giving the unique ID after sorting, I wanted to use the below way, and its advantage is that I can keep both IDs in id12. But the code doesn't work as I expect. id12 for the first observation is supposed to be 135205439, not 135205440. I hope that there is a simple fix for this.

Code:
        clear 
        input id1 id2
        
        1352     5439
        5386    9615
        4359    8139
        
        end
        
        gen id12= id1*10^5 + id2
        format id* %16.0f
        
        list
        
     |  id1    id2        id12 |
     |-------------------------|
  1. | 1352   5439   135205440 |
  2. | 5386   9615   538609600 |
  3. | 4359   8139   435908128 |