How can I get a sequence of numbers 1,2,3,4 from the model below, using code in ArcGIS Desktop to do this in the Field Calculator?

ObjectID   POINT_X	  POINT_Y   N_Ordem
179705	277537,5975	167114,8149	1
179705	277546,9257	167111,2111	2
179705	277541,5203	167097,2191	3
179705	277522,8641	167104,4261	4
179705	277528,2697	167118,4183	5
179705	277537,5975	167114,8149	6
179708	277458,3343	167031,5693	1
179708	277452,8895	167017,5923	2
179708	277443,5715	167021,2221	3
179708	277449,0163	167035,1991	4
179708	277458,3343	167031,5693	5
179712	277482,4411	167038,2495	1
179712	277476,9701	167024,3099	2
179712	277467,6521	167027,9397	3
179712	277473,1321	167041,9029	4
179712	277482,4411	167038,2495	5
179717	277543,0029	167128,8071	1
179717	277537,5975	167114,8149	2
179717	277528,2697	167118,4183	3
179717	277533,6747	167132,4109	4
179717	277543,0029	167128,8071	5