Formula to put 1 in the first value and 0 for the rest. Duplicate dataset

I'm looking for a smart way to indicate only one row with duplicated values. I need it to help my pivot table a little.

Id Description Estimation(h) Formula
1  Desc1       20            1
1  Desc2       20            0
1  Desc3       20            0
2  Desc4       30            1
2  Desc5       30            0
2  Desc6       30            0